iqg heating glassiqglass.com/images/downloads/iqg_insights.pdfiqg heating glass insights ... found...

IQG HEATING GLASS

INSIGHTS

I Q G L A S S , I N C .The Ult imate in Radiant Heating Glass Systems

I Q G l a s s , I n c . • t e l e p h o n e : 8 8 8 . 5 0 8 . 6 7 11 • f a x : 6 1 5 . 6 3 4 . 2 5 0 0 • e m a i l : i n f o @ i q g l a s s . c o m • w e b : w w w. i q g l a s s . c o m

mailto:[email protected]

mailto:[email protected]

http://www.iqglass.com

http://www.iqglass.com

Introduction

IQG Radiant Heating Glass (IQG) is an electrically heated glass providing a unique problem-solving solution to sev-eral construction difficulties.

The concept of electrically heated glass is based on the electric characteristics of Low-E glass. The electrical character-istics of low-e glass were used for the first time in 1986 in Europe.

IQG is applied in several hundreds of applications so far. This innovation has been installed in a number of office buildings, restaurants, hotels, corporate headquarters, public swimming pools... but also in private homes, conserva-tories and winter gardens.

IQG can be used in all standard window structures, whether they are in wood, PVC, aluminum or steel.

IQ Glass, Inc. has nothing but most enthusiastic and satisfied users of heating glass. Technical solutions that seemed impossible in the past have become possible since the use of heating glass.

IQG eliminates all the difficulties and disadvantages that are caused by the thermal insulation capacities of glass. The heating glass surface eliminates the sensation of cold draft, it prevents surface condensation, it compensates the loss of temperature through the glass surfaces and it makes snow and icing on the outside of the window melt when set-up for that purpose. Creating comfort is one of the main advantages of heating glass.

IQG is primarily used as a sole heating source but it can easily be combined with existing heating systems that are incorporated to the building structure, such as floor heating, ceiling heating and heating panels. IQG increases living comfort by eliminating the sensation of cold draft. This effect is reached by raising the surface temperature of the glass to the same level as the air temperature of the surrounding objects. IQG eliminates the necessity of radiators near the windows, therefore achieving dramatically more living space. One of the typical characteristics of heating glass is that it allows you to lower the room temperature by several degrees (3 ºC or 9 ºF) without any impact on the comfort of the living surroundings. This phenomenon means an important energy saving in comparison with the traditional glass and heating systems.

In the sections ahead we will provide a more in depth look at the characteristics of traditional glass vs IQG Radiant Heating Glass (IQG).

Welcome to the ultimate comfort!

IQ Glass, Inc.

C o p y r i g h t © I Q G l a s s , I n c . A n I n t r o d u c t i o n t o I Q G R a d i a n t H e a t i n g G l a s s P r o d u c t s

1

Traditional Glass

Windows play an important role in creating living comfort. This is why the amount of glass surfaces in public and private buildings has increased during the last years. Glass technology has improved considerably: the application of energy saving low-e glass is increasing. Despite the advance in this technology, the low surface temperature of glass still remains a problem.

IQG Radiant Heating Glass (IQG) offers a solution to this problem. Heating glass allows you to raise the glass sur-face temperature to a level on which the disadvantages of cold radiation disappear.

Light Transmission and Energy Transportation

When the inside temperature of a house is higher than the outside temperature, heat will filter to the outside. The windows are part of the building with the lowest insulation capacity. The temperature losses through the windows usually are substantial.

In a traditional detached house, glass surfaces are responsible for about 20 up to 25 % of total heat losses.

Increasing the number of glass plates may improve the thermal insulation capacity but every additional glass plate reduces light transmission and increases the price.

Instead, low-e Glass can be a valuable alternative. The light transmission factor is the same as for normal glass, but it reflects the thermal radiation back to the inside of the house and it offers protection against extreme sun heating dur-ing the summer.

Low emission glass reduces temperature losses via thermal radiation. The convection and the heat induction in the space between the glass panes of an insulating entity can be reduced by filling the space with a low conduction ca-pacity gas such as Argon (Ar) or Krypton (Kr). IQ Glass, Inc. uses Krypton, which reduces heat losses by about 10 % up to 30 %.

Figure 1 - Low-e Window


2

Radiant Heat

Inside

Visible LightOutside

Heat losses through materials such as glass are characterized by a U-value (insulation value).

GLASS STRUCTURE U-VALUE (W/M 2K) U-VALUE (BTU/HR FT 2 ℉)

Single Glass 5.8 1.021

Insulated Glass Unit (IGU) 3.0 0.528

IGU with Triple Glass (gas-filled) 1.8 0.317

IGU with Low-E Glass 1.3 0.229

IQG Insulated Glass Unit (*) 0.84 0.148

Table 1 - U-Values

(*) The center pane U-Value of IQG is 0.162 Btu/hr f t 2 ℉ (0.92 Watt/m2K). Including the edge effect of the super-spacer reduces the U-Value of the complete IQG IGU to an average value of 0.148 Btu/hr f t 2 ℉ (0.84 Watt/m2K).


3

Radiant Heating Systems

IQG is a radiant heating system. Radiant systems provide unique, cost-effective approaches to addressing numerous conditions affecting human thermal comfort, as primary or hybrid systems. Radiant systems are used to condition space, often in the traditional way that convection systems must do, by their nature, to produce a selected air tem-perature. However, radiant heating systems may also be used to heat people in comparison to space. The idea is that the occupied air mass is heated to a lower dry-bulb air temperature than with a convection heating system as long as the occupants are radiantly heated. The idea is to save energy or to overcome otherwise adverse local comfort condi-tions.

Radiant heating systems provide the opportunity to provide comfort at lower ambient air temperatures. As explained by Watson & Chapman1, the presence of a radiant field, or MRT, characteristic of all radiant systems, normally results in comfort at a 4 ℉ to 6 ℉ lower dry-bulb air temperature than if a convection heating system was used. A 1 ℉ air temperature reduction results in a 3 % energy reduction. In reference 1 it was highlighted that a 12 to 18 % energy reduction is a minimum expectation for a radiant heating system in comparison to a convective system providing equivalent comfort.

The ability to sunbathe on a calm spring day is a dramatic example of the role that radiant energy can play in provid-ing thermal comfort at a lower ambient dry-bulb air temperature. Another equally striking example is that of skiers in swimsuits on days when the air temperature is around freezing point and the snow is still crisp and fresh. The dry, clear, thin high-altitude air; strong late-spring sun; and snow covered surface all combine to enable the high intensity radiant field make the human body feel comfortable in otherwise cold conditions. These examples are illustrative of the important role that radiant heat transfer can play in providing human thermal comfort.

Radiant heat transfer theory is not included in this issue. An explanation on the subject ‘radiant heat transfer’ can be found in the Radiant Heating and Cooling Handbook by Watson and Chapman1.


4

1 Radiant Heating and Cooling Handbook, McGraw-Hill, Richard D. Watson & Kirby S. Chapman, 2002

Comfort and Causes of Discomfort

What is Thermal Comfort?

The American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55 (1992) de-fines thermal comfort as “the condition of mind that expresses satisfaction with the thermal environment”. This defi-nition loosely translates to the question whether the occupant feels too hot, too cold, or just right.

The six primary variables used to predict thermal comfort are activity level, clothing insulation value, air velocity, humidity, air temperature and mean radiant temperature (Fanger, 1967):

a) For most design situations, the room usage dictates the activity level and clothing insulation value. For example, an office situation implies sedentary activity with business attire. In contrast, an exercise room implies a high activity level with shorts and T-shirt.

b) In addition, the humidity depends on the heating or cooling system, generically referred to as thermal distribu-tion system, for the entire building, which may not be controlled at the room level.

c) Usually, the air velocity is maintained at a level that avoids a draft yet provides the necessary fresh air for the occupants.

d) In an individual room, the dry-bulb air and mean radiant temperature (MRT) are two variables that the design engineer may control on an individual room level. The dry-bulb air temperature measures the temperature of the air in the room. The mean radiant temperature is a measure of the radiant energy exchange. Most thermal distri-bution systems are designed to maintain a baseline air temperature. Since radiant heat energy does not directly heat air, the air temperature does not take into account the radiant energy exchange in a room. The mean radiant temperature indicates the average temperature of the surfaces relative to the occupant.

Figure 2 - Analyzing Thermal Comfort at Two Locations in the Same Room


5

- 0.4 ℉

68 ℉

Consider the room with a large cold window shown in figure 2. The room is at a uniform air temperature of 68 ℉. At the back of the room is a large window to the outside at - 0.4 ℉. An occupant at point 1 could be thermally comfort-able, but the occupant at point 2 could complain of feeling chilly. The air temperature at both points is the same, so the room thermostat does not give the answer. The difference between the two points is the radiant energy exchange. Point 1 is sheltered from the full extents of the net radiant window and is subject to much larger radiant energy losses. Comparatively, this means the MRT at point 1 will be higher than at point 2.

Examples from Watson & Chapman2 show that radiant heating systems lead on average to higher MRT values in a room than forced-air heating systems.

The operative temperature combines the air and the mean radiant temperature into one numerical quantity. It is a measure of the body’s response to the convection and radiant energy exchange.

Historically, heating and air-conditioning design philosophies have focused on obtaining a specific indoor tempera-ture for a given design air temperature. If the design air temperature was achieved in a room, then the occupants were considered thermally comfortable. This approach does not differentiate convective energy from radiant energy exchange. Therefore, the design air temperature may not accurately represent the occupant’s thermal comfort. One of the most common examples of the air temperature misrepresenting the occupant’s thermal comfort is standing out-side on a cool, calm day. As shown in figure 3, the air is a chilly 50 ℉. Without any unusual weather patterns, the out-door surroundings are approximately equal to the air temperature. The occupant loses energy via convection to the cooler air shown by the thin wavy lines around the ‘air cloud’ and radiation to the cooler surrounding surfaces shown by the thin horizontal lines from the occupant’s right to the tree. With the sun shining, the occupant receives additional energy from the sun via radiant energy shown by the thick straight lines directed to the occupant’s left. The occupant feels thermally comfortable due to the energy balance between the energy lost to the air and the slow-ing of energy loss by the sun plus internal heat generation. The mean radiant temperature would be above the air temperature of 50 ℉.

Figure 3 - Simplified Energy Exchange Diagram for a Sunny Day


6

2 Radiant Heating and Cooling Handbook, McGraw-Hill, Richard D. Watson & Kirby S. Chapman, 2002

50 ℉

When a cloud covers the sunshine and blocks some of the radiant energy from the sun as shown in figure 4, the occu-pant’s energy gain decreases. The occupant is still losing energy to the air and surroundings. In this situation, the amount of energy lost to the air and surroundings is greater than the energy gained from the sun. Due to the energy imbalance, the occupant begins feeling chilled. Although the mean radiant temperature may be above the air tem-perature, the occupant is still thermally uncomfortable, due to a net energy loss.

Figure 4 - Simplified Energy Exchange Diagram for a Cloudy Day

The use of curtains with IQG also follows this principle. When the curtains are drawn you might feel a slight level of discomfort/chill but this feeling completely and quickly disappears when the curtains start to radiate the heat. The same happens when you’re sunbathing and a cloud starts covering the sun. You might feel chilly for a few seconds until the cloud itself starts to radiate the heat and you get rid of that chill factor again.

Remark: Instead of using thick curtains to block the cold out, you can now use thinner curtains just to keep the light out!

The differences in MRT level between IQG windows and traditional double pane units with radiators is experimen-tally proven in one of the tests referred to at the end of the document.


7

50 ℉

Causes of Discomfort

Asymmetrical Radiant Temperature

Figure 5 - Asymmetry Radiant Temperature

Figure 5 shows the results of a test that checked the effects on the sensation of comfort with different systems of asymmetric radiant temperature (source: ASHRAE handbook 1997 - Fundamentals - American Society of Heating, Refrigeration and Air-conditioning Engineers).

Asymmetric or non-uniform radiant temperature is caused by cold windows and non insulated walls. In living rooms, conservatories, restaurants, offices, etc. asymmetric radiation due to cold surfaces during the cold seasons such as autumn and winter is the main reason of the sensation of discomfort.

The results of the study are:

• If the ceiling has a temperature of 18 ℉ (10 ℃) more than the rest of the room, there are on average 30 persons out of 100 who feel uncomfortable

• If the wall has a temperature of 18 ℉ (10 ℃) below the rest of the room, there are on average 10 persons out of 100 who feel uncomfortable

• If the ceiling has a temperature of 18 ℉ (10 ℃) below the rest of the room, there are on average 3 persons out of 100 who feel uncomfortable

• If the wall has a temperature of 18 ℉ (10 ℃) more than the rest of the room, there are on average 1 or 2 persons out of 100 who feel uncomfortable.

This leads to the conclusion that warm ceilings and cold walls produce a very negative effect on comfort. On the con-trary, warm walls have a positive influence on comfort. This means that heating glass will contribute significantly to the increment of comfort.


8

Vertical Temperature Gradient

Figure 6 - Vertical Temperature Difference

Under normal conditions, the air temperature of a room raises from the floor to the ceiling. In the case of a pro-nounced temperature gradation, this causes great discomfort. Heating systems based on convection, such as convec-tors or radiators make the warm air rise while it is being replaced by cold air. This system causes a most annoying air circulation, and it furthermore creates a temperature difference between the floor and the ceiling.

IQG is based on radiant heat. Radiant heating systems heat up the objects, not the air! They eliminate this convection stream, in order to keep an almost constant air temperature once all the objects have the same temperature.

Figure 6 shows the percentage of unsatisfied persons in relation to the temperature differences between head and feet. If the difference is about 5.4 ℉ (3 ℃), there are about 5 % unsatisfied people.

Figure 7 - Vertical Temperature Gradient

Figure 7 shows the vertical temperature gradient between glass heating and the traditional heating systems with sin-gle glass.


9

Influence of the Glass Surface Temperature on Comfort

Figure 8 - Influence of Glass Temperature on Thermal Comfort

There are two reasons why an individual experiences discomfort near cold glass windows: heat loss through radia-tion via the skin which is experienced as ‘a cold glow’ and cold window surfaces which cause an air circulation.

In an attempt to reduce these effects, radiators are placed under or in front of the windows. The actual air or room temperature is not the only aspect that contributes to the sensation of warmth and cold; for comfort, also the thermal radiation of surrounding walls has an important impact. In fact, the temperature of surfaces such as glass windows, have more impact on comfort than the air temperature. If the temperature of the glass is lower, air temperature should be raised in order to maintain the level of comfort. This evidently results in more energy consumption.

The glass surface temperature of the window is influenced by both the heat loss ratio (U-value) and the outside air temperature. A better U-value results in a higher inside temperature of the glass.

The cold glass problem can be resolved by using IQG. If the temperature of all the objects is almost identical, room temperature can even be reduced by about 5.4 ℉ (3 ℃) whilst maintaining the same comfort level.

Figure 8 shows for several U-values, the connection between the glass surface temperature and the outside air tem-perature.

Comfort Zone

Thermal comfort depends mainly on a combination of the air temperature and the average radiant temperature. The expression ‘comfort zone’ was created to refer to these combinations of air temperature and average radiant tempera-ture which makes one feel comfortable. There is a dedicated comfort zone for every application, calculated by Profes-sor Fanger in 1982. Figure 9 represents the comfort zone.

The average radiant temperature depends on the different surface temperatures of the distinct walls, the dimensions and the shape of the surfaces and the place of the individual in relation to the different surfaces.


10

Figure 9 - Representation of the Comfort Zone

The reports of Fanger show that the optimum temperature for glass surfaces is situated between 68 ℉ (20 ℃) and 86 ℉ (30 ℃). IQG ensures via a combined system of thermostats, glass surface temperature sensors and microproces-sors that this will always be achieved. The control system is explained in section “Control and Regulation of IQG”.


11

IQG Radiant Heating GlassElectric low-e glass that can be heated when the outside temperature lowers is one of the most recent developments in the area of glass technology.

Figure 10 - Schematic of an Electrically Heated Window

IQG Radiant Heating Glass (IQG)

Low emission glass is at the base of ‘heating glass’, for it is the low emission coating that heats the glass by its electric resistance. The concept is applied in insulating glass panes, laminated elements and mirrors.

The production of electric glass is not very different from traditional insulating glass. IQG is composed of two or more low emission glass panes that are connected one to another by a superspacer. The connected components are closed with a material that is resistant to gas and humidity. The interior space is filled with an inert gas with a very low heat conduction capacity.

The main difference between ordinary glass and electrically heated glass is the electric feeding: two electrodes, con-nected to electric wires are fixed to the low emission coating of the inner pane. Electric glass functions on a low ten-sion circuit: by using a transformer, the glass is adapted to 230 V or 110 V depending on the region and/or require-ments of the project.

The conducting coating is always used on the inner side of the interior pane. Both panes of the electrically heated glass are made of tempered or safety glass. Its durability is relevantly longer than for ordinary glass. Toughened glass is about 7 times stronger than ordinary glass. If it is broken, it falls apart into thousands of small pieces. This com-pletely interrupts the conduction of the coating, and makes the tension and current disappear.


12

Applications of IQG

The most important and frequent application of IQG is in the building industry, in the private and commercial sec-tors. IQG can be used as a sole heating system or in conjunction with an existing heating system. IQG is very popular in homes, conservatories, restaurants, etc.

IQG eliminates condensation. One of the most famous applications with this purpose is the use of IQG in the Terra-Cotta Army museum in China.

Heating glass is the only way of solving problems caused by low surface temperatures of glass windows. In geo-graphically cold regions, where icing is frequent, IQG is used to defrost the windows in public swimming pools, pub-lic buildings and houses, as well as to melt snow and ice on glass roofs and atriums. In these cases, the heat is radi-ated towards the outside.

Since IQG uses radiant heat, there is almost no convection. Therefore, it is used in ‘clean rooms’ of pharmacological enterprises, laboratories and hospitals.

IQG can be used as an anti-burglary protection system. Even before the burglar gets through the window, the alarm will start working. The alarm system is coupled to the outer coating of IQG. The alarm system is continuously in op-eration so you can’t forget to turn the alarm system on. IQG can be equipped simultaneously as anti-burglary protec-tion and as a heating system.

There are several other applications possible other than heating windows and transparent roofs. Those applications are found essentially in the industrial area. Amongst them, there are applications such as the windows in the cabin of forklift trucks, ship windows (especially the windows of the commanding cabin), anti-condensation glass for refrig-erators and blood bank refrigerators, wind screens and windows of cars and trains, radiant heaters and heating mir-rors. IQG can also be used in fish tanks.

The Efficiency of IQG

In the early days of heating glass a lot of people were firmly convinced that energy consumption increases with heat-ing glass. Several investigations prove the opposite.

According to reports and tests, realized by Laborelec Brussels and by CEBTP France, the efficiency (the part of the energy input that is pulsed into the room as heat) of an IQG window is excellent, at least 93 %, due to the low emis-sion glass. This means that the produced energy is used to heat the room with a minimal amount of losses. Efficiency is variable, depending on the composition and the structure of the glass pane, the glass temperature, the outside air temperature and the room temperature.

In the section ‘IQG Testing’ of this document it is highlighted that 32 % to 38 % less power is required with IQG com-pared to a normal double glazing unit & radiator to obtain the same resulting or operating temperature.


13

IQG as a Heating System

The main objective of IQG is to be a heating system and to create comfort. It can easily be used as a sole heating sys-tem or it can work in conjunction with other heating systems.

Power Requirement for Different Applications

The desired power of IQG depends upon its application. The following table shows the advised values of power den-sity that are applied in different situations.

APPLICATION POWER DENSITY RESULTS

Anti-condensation 50-100 Watt/m2

4.65-9.28 Watt/ft2

• All the surfaces of the room have the same temperature• Draft caused by cold surfaces is eliminated• The cold glow of glass surfaces is eliminated• No condensation on glass surfaces

Heating system 100-300 Watt/m2

9.28-27.87 Watt/ft2

• Glass windows can be used as sole or secondary heating• Heating glass can be set on an exact temperature by

means of a microprocessor

Special applications 50-500 Watt/m2

4.65-46.45 Watt/ft2

• Melting of snow and ice on glass roofs• Defrosting of windows in control towers, vehicles, navi-

gation cabins, etc.• Heating of terraces, winter gardens, spaces with glass

roof• Heating of greenhouses• Temperature of glass surfaces depends on the applica-

tion

Table 2 - Power Density in Different Situations

The normal operating range is 2.79-23.23 Watt/ft2 (30-250 Watt/m2). The average power is about 4.65 Watt/ft2 (50 W Watt/m2) per year when IQG is used as a sole heating system.


14

The Effect of the Glass Surface on Power

Figure 11 shows the estimated required glass surface if glass heating is used as the principal heating system.

Figure 11 - Necessary heating glass surface per floor space

In the majority of domestic applications IQG can be used as the main heating system. It is important to regulate the glass surface temperature in a way that it is situated within the comfort zone (between 68 ℉ [20 ℃] and 86 ℉ [30 ℃]).

Calculation of the maximum available power: Pmax = Glass (m2) x 250 Watt/m2, with• Pmax: maximum power (Watt)• Glass: glass surface (m2)

For every project a detailed heat loss calculation will be done in order to obtain the exact amount of heat loss throughout the building. The amount of power produced by the heating glass has to overcome this heat loss value. In some rooms like a hallway or bathroom there won’t be enough window surface available to heat up the room so of-ten we suggest to use IQG Heating Mirrors.

Combining of Different Heating Sources

There are no limitations as far as combining IQG with different heating systems. Very often the combination of differ-ent systems offers a better result than one single system, especially as far as the living comfort is involved.

When different heating systems are used, the main problem is to decide which task will be conferred to each system. In order to dimension correctly the electrically heated glass, the following questions should be answered:

• Is the glass heating the main heating system, floor, ceiling and radiator heating being used mainly as sources of temperature comfort?


15

Floor (m2)

Gla

ss (m

2 )House

Condo

• Is the glass heating applied primary as a source of comfort in addition to other systems?• Is glass heating used as temperature regulator in addition to another system used to produce basic heating?• Is glass heating only used when someone is present?

When dimensioning the different heating systems, the heat generated by glass heating may be deduced from the power generated by other heating systems.


16

Electrical Power of IQG

Figure 12 - Electrical Power in Function of the Glass Surface Temperature

Figure 12 shows the specific power of IQG with respect to the glass surface temperature for different ambient air temperatures. These values are of indicative value.


17

Thermal Characteristics of IQG

U-Value of IQG

The Uw-values and Uf-values were calculated following standard EN ISO 10077 by Glaverbel in September 2006. Comparisons were made between the use of an aluminum spacerbar and the Edgetech Superspacer.

The composition of the glass was:

• 1/4” (6 mm) Top NT - 0.63 “ (16 mm) Krypton with Superspacer - 1/4” (6 mm) Top NT Ug = 0.1761 Btu/hr f t 2 ℉ ( 1.0 W/m2K)

• IG unit size: 48.43” x 58.27” (1230 mm x 1480 mm)• Uf-values measured according to standard EN ISO 10077

To calculate Uw several frames have been included in the simulation, i.e. wood with Uf = 0.2467 Btu/hr f t 2 ℉ (1.4 W/m2K), PVC with Uf = 0.3347 Btu/hr f t 2 ℉ (1.9 W/m2K) and aluminum with Uf = 0.3524 Btu/hr f t 2 ℉ (2.0 W/m2K).

The Uw-value of IQG is measured following standard EN 10077.

The Uw-value is:

Uw: Value of the complete windowUf: U-value of the frameAf: Visible surface of the frameUg: U-value of the glass unit

Ag: Visible surface of the glass unit ψ: Linear transmission coefficientL: Perimeter of the glass


18

The linear transmission coefficient represents the thermal flux caused by the interaction between the frame and the edge of the glazing unit. The effect of the linear transmission coefficient and the effect of the superspacer were mod-eled via Finite Element Analysis.

Table 3 represents the Uw-values for IQG and the three different frames.

Uw

Btu/hr f t 2 ℉

(W/m 2K)

WOOD

Uf = 0.2467

(1 .4 )

PVC

Uf = 0.3347

(1 .9 )

ALUMINUM

Uf = 0.3524

(2 .0 )

Aluminum 0.2290 (1.3) 0.2555 (1.45) 0.2713 (1.54)

Superspacer 0.2202 (1.25) 0.2467 (1.40) 0.2502 (1.42)

Psi Aluminum 0.0076 (0.043) 0.0074 (0.042) 0.0072 (0.041)

Table 3 - Results for Uw in Btu/hr ft2 ℉ (W/m2K)

Table 4 represents the Uf-values for IQG and the three (3) different frames.

SPACER GAP ARGON

100 %

ARGON

90 %

KRYPTON

100 %

KRYPTON

90 %

0.39” (10 mm) 0.2449 (1.39) 0.2520 (1.43) 0.1621 (0.92) 0.1815 (1.03)

0.47” (12 mm) 0.2150 (1.22) 0.2220 (1.26) 0.1656 (0.94) 0.1850 (1.05)

0.59” (15 mm) 0.1868 (1.06) 0.1942 (1.102) 0.1691 (0.96) 0.1891 (1.073)

0.63” (16 mm) 0.1885 (1.07) 0.1956 (1.11) 0.1691 (0.96) 0.1903 (1.08)

Table 4 - Results for Uf in Btu/hr ft2 ℉ (W/m2K)

If we just want to know the U-value of the IG unit with the superspacer effect included then we get a maximum U-value of 0.1621 Btu/hr ft2 ℉ - 0.0088 Btu/hr ft2 ℉ = 0.1533 and a minimum U-value of 0.1621 Btu/hr ft2 ℉ - 0.0211 Btu/hr ft2 ℉ = 0.1410 Btu/hr ft2 ℉ [U-value of 0.92 W/m2K - 0.05 W/m2K = 0.87 W/m2K and a minimum U-value of 0.92 W/m2K - 0.12 W/m2K = 0.80 W/m2K].


19

Thermal Characteristics of IQG

Figure 13 - U-values with Reference to Glass Surface Temperature

There are two (2) different approaches in order to define the thermal conduct of IQG:

• The first method consists in characterizing the thermal conduct by the U-value of IQG when it is not heated (or the productivity or efficiency of the glass heating).

• The second method consists in characterizing the thermal conduct by a variable U-value, (i.e. a U-value that changes in relation to the glass surface temperature and the outside air temperature).

Figure 13 shows the connection between the U-value (Y-axis) and the glass surface temperature (X-axis) for several values of the outside air temperature.


20

Control and Regulation of IQGIQG heating systems mostly use the control and regulation system as described in the section “Combined Thermostat-Microprocessor Regulation” to maintain the required level of comfort. Nevertheless, the other systems described in the sections below can be used if required.

Introduction

In traditional domestic applications, IQG is applied with a maximum power of 23.22 W/ft2 (250 W/m2). Since the required power is variable, during the day as well as during the year, the maximum power is not always required, and a power setting will be used. This setting can be implemented in several ways:

• based on an air thermostat;• based on a glass surface temperature regulation;

• based on a combination of an air thermostat and a glass surface temperature regulation.

Glass heating has a very low thermal inertness, which means that the heating and cooling processes of the glass are very fast processes. A discontinuous regulation, that implies a considerable lapse of time between the switching on and the switching off are disadvantageous to the comfort. During the periods when the glass heating is switched off, the glass cools down very fast and you experience the ‘cold glow’ of the glass. This means that the glass surface tem-perature should not experience extremes, and that it should never drop below a certain value.

Thermostat Regulation

In this type of regulation, the thermostat measures the air room temperature. In function of these measurements, the power of the glass heating is adjusted. The electrically heated glass is switched on or off until the indicated value is reached. This type of regulation can cause strong variations in the glass surface temperature, most of all when the temperature losses through the non-glass surfaces are small. During the periods of switching off, the glass cools down completely. The difference of comfort between the periods of activity and non-activity is enormous.

Microprocessor Regulation

This way of regulating the comfort is based on the glass surface temperature. A temperature sensor on the inside pane measures the glass surface temperature. The microprocessor checks the temperature six times per minute, and if necessary switches on or off the glass heating. With this type of regulation, the glass temperature suffers fewer ex-tremes, and that causes an increase in comfort. The consumption of electricity is reduced because this system makes it possible to maintain the glass temperature on a constant level using a lower power. Glass temperature can be ad-justed with a precision of 0.1 ℃. This type of regulation is only used when the purpose of IQG is comfort orientated or condensation prevention.


21

Combined Themostat-Microprocessor Regulation

This temperature regulation combines the advantages of the two previous regulation systems. The thermostat regu-lates the air- or room temperature according to the set value, while the microprocessor regulates the glass surface temperature. With this type of regulation, the glass surface temperature never goes below a previously adjusted value. However, glass surface temperatures may increase periodically when extra power is required in order to keep the air temperature on the set level. This regulation requires a microprocessor, a temperature sensor on the glass sur-face and a thermostat.

IQG heating systems most often use this control and regulation system to maintain the required level of comfort. At all times the aim is to keep all objects in the room including the glass surface at the same temperature. When the out-side temperature is very low it will take a certain time before the air in the room is affected by any temperature change outside. The glass surface on the contrary will immediately sense any outside temperature fluctuations. The sensor on the glass surface will send a signal to the microprocessor to report any temperature change and will ask for more or less power. This is a very efficient and quick system to maintain the level of comfort at all times.


22

Other IQG InformationCabling

For doors and pivoting windows, DORMA systems are used. DORMA systems allow the cabling to be built-in com-pletely invisible and safe. Also sliding and sashed windows can be provided with IQG. In the latter cases, the electric supply is guided by a cabling conveyor system or we easily provide electrical contacts on the frames so when intact IQG will be in operating mode or the system will be switched off when there is no longer contact made.

Warranty

IQ Glass, Inc. offers a 5-year limited warranty on the heated glass. All the performances of our produced units are tested for quality purposes.

An optional extended 5-year limited warranty can be purchased.

Electrical Specification of the Components

Power Circle of IQG

The electrical supply is delivered via a separation transformer: the glass is connected to floating mono-phase power. The contacts for the power circle are solid state switches, resisting to high switching frequency of about 600 switches/hour. The size of the transformer is project dependent and the required power is determined in a way to diffuse a maximum power of 23.22 W/ft2 (250 W/m2) on each glass pane.

Power Adjustment with Air Thermostat

When an air thermostat is used, the relation between the periods of switching on and off is adjusted with a minimum frequency of 1/120 sec.

Power Adjustment of IQG with Surface Temperature Measuring

The power of IQG is adjusted by measuring the surface temperature. The relation between the periods of switching on and off IQG is adjusted with a minimum frequency of 1/6 sec.

Minimum surface temperature adjustment (thermostat, microprocessor and temperature sensor)

The working principle is explained in the section on “Control and Regulation of IQG”. The relation between the peri-ods of switching on and off IQG is regulated. The minimum frequency for the air temperature regulation system is 1/120 sec. The minimum frequency for the surface temperature measuring is 1/6 sec. The microprocessor used is a temperature controller E5Cn of Omron. The temperature sensor is of the type PT100.


23

IQG in Swimming PoolsThermal comfort in indoor swimming pools is excluded without using IQG. Without IQG, one has to compromise between maintaining the building, the energy consumption and the comfort of the swimmer. IQG takes care of al-lowable lower air temperatures, less energy consumption and TOTAL COMFORT.

The Swimmer’s Comfort

The ideal relative humidity in an indoor pool is about 70 %. When relative humidity is low, it generates a sensation of cold, caused by the fast drying of the skin. When relative humidity is high, it causes an unpleasant suffocating sensa-tion, due to too high temperature and humidity level. During the winter, the double glass panes, even with a room temperature of 82.4 ℉ (28 ℃) in the swimming pool, irradiates an intense ‘cold glow’ that makes the swimmer shiver when he comes out of the water.

Energy Consumption

If the relative humidity level is high, damping level is low and less energy is required to dry the air. To maintain the same level of thermal comfort, the air temperature may be reduced, even when the relative humidity level is increas-ing.

Until now, the best thing to do was to adapt the relative humidity level (RHL) in relation to the outside air tempera-ture by means of a dehumidifier:

• Summer: 70 % RHL

• Spring and fall: 60 % RHL• Winter: 50 % RHL

If the relative humidity level is reduced with 10 %, energy consumption increases by 14 % to keep the swimmers warm. When using IQG, the relative humidity level during the winter period may be maintained at 70 %, without generating condensation danger. This level of humidity can therefore be maintained throughout the year. Further-more, this generates an energy saving of about 30 %, and the comfort is better than ever. Condensation is avoided, and the cold radiation of the glass has become radiant heat.

Maintenance of the Building

If the relative humidity level is high, it generates a risk of surface condensation on cold walls such as glass surfaces. This risk increases if thermal insulation is not good and outside air temperature drops.

Condensation on double pane glass is generated under the following conditions:

• 70 % RHL - outside air temperature 53.6 ℉ (12 ℃)• 60 % RHL - outside air temperature 42.8 ℉ (6 ℃)• 50 % RHL - outside air temperature 32 ℉ (0 ℃)


24

Figure 14 - Condensation on a Cold Wall

Figure 14 shows when condensation appears with respect to the outside air temperature and the relative humidity.

The three determining factors of condensation are:

• Outside air temperature• Relative humidity level• U-value:

• Single pane glass = 1.021 Btu/hr f t 2 ℉ (5.8 Watt/m2K)• Double pane glass = 0.528 Btu/hr f t 2 ℉ (3.0 Watt/m2K)• Triple pane glass (gas filled) = 0.317 Btu/hr f t 2 ℉ (1.8 Watt/m2K)

• Low-e glass = 0.229 Btu/hr f t 2 ℉ (1.3 Watt/m2K)• IQG = 0.148 Btu/hr f t 2 ℉ (0.84 Watt/m2K)

Condensation water can damage the window, the floor, and even the double pane glass. When relative humidity level is 70 % and outside temperatures are extremely low, IQG is free of condensation.


25

IQG and Indoor Swimming Pools

Compromises are not necessary with IQG. The air temperature of the swimming pool may be brought to a lower level in a situation of higher relative humidity level.

• There are no condensation problems, which is a positive element for the conservation and maintaining of the build-ing.

• An absolutely superior comfort level, generated by the glass radiant panes when air temperature is lower: it limits energy consumption.

• No more condensation with chlorine deposit (white mould) on the glass.• Global comfort for the swimmer, since cold glass surfaces are eliminated.


26

IQG MirrorTo settle once and for all with condensation on mirrors, electrically heated IQG Mirrors are the solution with which one can enjoy the comfort and the pleasant radiant warmth. As a result of its space saving character, the IQG Mirror is the problem-solver for the interior designer, the decorator and the living-or shop organizer.

Characteristics

• The IQG Mirror is heated homogeneously over the entire surface

• The IQG Mirror has a 0.51” (13 mm) thickness• The IQG Mirror is ultra safe: the mirror and the heating glass pane are layered onto each other, so that in case of

breakage, instead of falling apart, the splinters of the mirror stick together. Electrocution is excluded.

Technical Data

Mirror layout

Figure 15 - Mirror layout


27

Voltage

230V or 110 V (or if needed, via transformer).

Power

There are different power settings available depending on the requirement. The IQG Mirror can be used to avoid condensation, to act as a heating system in bathrooms or in places where there is not sufficient amount of heating glass available or as a combination of the two.

The different settings are:

SETTINGS Watt/f t 2 ℉ Watt/m 2 ℃

Anti-condensation 9.29 +- 80.6 100 +- 27

Radiant heat 18.58 - 32.52 +- 104 200 - 350 +- 40

Heating 32.52 - 46.45 +- 104 to +- 129.2 350 - 500 +- 40 to +- 54

Maximum power 46.45 +- 129.2 500 +- 54

There are several power system controls available:

• Minimum/maximum by dimmer

• Thermostatic regulation• Main switch (on/off)• Domotics

• Movement sensor• Etc.

Dimensions

• All our mirrors are made-to-measure• Max dimensions: 78.74” x 118.11” (2 m x 3 m)• Total thickness: 0.51” (13 mm)

• Construction and finish: as desired


28

IQG AlarmIQ Glass, Inc. gives a new dimension to anti-burglary security. By connecting IQG to an existing alarm system, your windows and glass panes now really are burglary-detecting.

The glass consists of an exterior glass pane, an air cavity and an interior glass pane.

The exterior pane consists of hardened safety glass. This glass is provided with an alarm coating based on neutral metal oxides. In addition, this hardened pane is 7 times stronger than traditional glass.

The air cavity between both glass panes is being protected against humidity by an insulating resin and thermally interrupter spacerbar.

The interior pane consists of a multi-layer anti-burglary safety glass. This pane can also be constructed in the heating version.

It is the coating of the exterior pane that is invisibly connected to the alarm system.

The hardened exterior pane can only be broken by violence. By interrupting the alarm coating, the pane’s resistance changes, which makes the alarm go off. Once the alarm is active, the burglar is still front of a laminated anti-burglary interior pane. As you already know, this pane stays, after breakage in its position and forms an impenetrable web of splinters.

The alarm system can be switched on at all times, even if you are in the building. The alarm glass is insensible to movement in the house, in contrast with detectors. The alarm only reacts if the glass gets broken. From now on your pet can easily walk around (alarm switched on) in your home without causing the alarm to go off. The glass forms, as it were, an invisible shield around your home.


29

IQG LaminatedFor many applications laminated glass is a necessity. Think of the wind shields of cars, roof glass, floor glass, anti-burglary and bullet proof glass, etc. The main objective is that in case of breakage, no glass splinters are released.

IQG can also be applied in laminated glass. An example is found in keeping ‘cold room’-panes condensation free, without the temperature of the ‘cold room’ being influenced.

Many forklift trucks are constructed with heating glass in order to avoid condensation problems when driving in and out of the deep freezing.

Even in the shipbuilding industry ice deposit and condensation are eliminated by laminated heating glass, and this as well at the inner as at the outer side.


30

IQG TestingDue to our innovations, the quality and characteristics of our ‘heating glass’ improve constantly. The following tests from 1997 and 1990 have been performed with lower performance glass. IQG’s U-value has since been improved to 0.148 Btu/hr f t 2 ℉ (0.84 Watt/m2K), but the general conclusions are still valid.

Testing by CEBTP

Introduction

CEBTP is a French Test Center that performed tests on IQG in 1997. CEBTP is part of the Ginger Group and is special-ized in testing and certification of construction products.

Testing

Double pane units in hardened glass equipped with a low-e coating with a low emission and filled with Krypton for 80 % were used. The tests measured the thermal performances of IQG and a comparison was made between IQG and traditional double pane units and a radiator in a bi-climate room. Once the intrinsic values of IQG were measured, these values were used to validate the numerical simulation models used. The simulations were performed using a traditional two-level house model and a conservatory.

Simulations

All housing characteristics such as wall type, ventilation, occupants, house environment and climate details (mete-orological values) were incorporated in the thermal model. The outside temperature was kept constant at 19.4 ℉ (-7℃) , 32 ℉ (0 ℃) and 50 ℉ (10 ℃) whilst maintaining the resulting temperature (the average of the air temperature and the average radiant temperature MRT in the center of the test pane) at 69.8 ℉ +- 0.54 ℉ (21 ℃ +- 0.3 ℃). The air temperature, the average radiant temperature and the surface temperature of every object were obtained. The re-quired power to maintain the 69.8 ℉ (21 ℃) resulting temperature was measured for both situations: IQG and tradi-tional double glazing unit with a radiator.

Results

Te = external air temperature in ℉ (℃)Pch = average heating power in WattTa = air temperature in ℉ (℃)Tr = average radiant temperature in the center of the pane in ℉ (℃) = MRTTc = resulting or operating temperature Tc=(Ta+Tr)/2


31

Te Pch Ta Tr Tc

19.4 (-7) 801 68.7 (20.4) 70.3 (21.3) 69.6 (20.9)

32 (0) 587 69.2 (20.7) 70.5 (21.4) 69.8 (21.0)

50 (10) 292 70 (21.1) 70.5 (21.4) 70.1 (21.2)

Average 560 69.4 (20.8) 70.5 (21.4) 69.8 (21)

Table 5 - Required Power for IQG in House Model

Te Pch Ta Tr Tc

19.4 (-7) 1154 71.6 (22.0) 66.5 (19.2) 69 (20.6)

32 (0) 875 71.4 (21.9) 67.4 (19.7) 69.4 (20.8)

50 (10) 471 71 (21.7) 69 (20.6) 70 (21.1)

Average 830 71.4 (21.9) 67.8 (19.9) 69.6 (20.9)

Table 6 - Power Required for a Traditional Double Pane Unit and Radiator in House Model

Conclusion

• 32 to 38 % less power required with IQG compared to a traditional double pane unit & radiator to obtain the same resulting temperature of 69.8 ℉ (21 ℃).

• With traditional double pane units & radiator the air temperature was 71.6 ℉ (22 ℃) in order to obtain a resulting temperature of 69.8 ℉ (21 ℃). The air temperature in the case of IQG was lower than 69.8 ℉ (21 ℃) as a result of pure radiant heat, resulting in better energy efficiency.

• With IQG, the average radiant temperature is substantially higher than the air temperature. With traditional double pane units & radiator, the air temperature is much higher than the radiant temperature. This effect inevitably re-sults in more power required to heat up the air using a traditional radiator. Since the radiant air temperature is much higher than the air temperature with IQG, the air temperature can be lowered whilst remaining the same comfort level for the occupants.

• The surface temperatures were obtained for all the objects. The surface temperature of all objects using IQG was much higher and closer to the resulting temperature than the surface temperature of all objects using a traditional radiator and double pane units. This dramatically improves the comfort level.


32

The main advantages of IQG are the improvement of living comfort and energy conservation.

Since the average radiant temperature (MRT) is very close to the air- or room temperature, the radiant effect of the glass (for a temperature of 77 ℉ to 68 ℉ [25 ℃ to 20 ℃]) can be compared to low intensity sun radiant heat. It elimi-nates completely the effects of the cold glass surfaces and reduces air drafts, caused by convection.

When IQG is not powered up, the U-value of the IG unit is 0.148 Btu/hr f t 2 ℉ (0.84 Watt/m2K). The two layers of low emission coating, the Krypton filling and the superspacer are responsible for this low value.

When the heating system is switched on, the heat losses are smaller than those of a traditional glass system. In a tra-ditional house, they are about 32 % to 38 % lower and 7 % to 15 % lower in conservatories.

In conservatories, the need of heating depends mainly upon the comfort experienced by the users. The radiant com-fort that is created by IQG is, for an equivalent air temperature, much more comfortable than a much higher tempera-ture in compensation of the cold glass surface. The need of effective heating in a conservatory with IQG is signifi-cantly lower than the calculated quantity.

The U-value increases when outside air temperature goes down, because the considerable temperature differences cause a convection stream in the krypton blanket between both glass panes. Since the U-value of heated glass in-creases with the heating capacity, it is to be recommended in spaces with important glass surfaces: about 1/3 of the floor surface for houses and 1/2 of the floor surface for conservatories.

Testing by Laborelec

Introduction

The tests performed by Laborelec in Belgium in 1990 were performed by using an early version of our IQG Radiant Heating Glass, using a double pane unit of IQG hardened glass with air filling. The tests done led to a report on the Determination of Thermal Characteristics of Heating Glass in a Bi-Climate Room”

Test Results

The tests in the bi-climate room demonstrated that IQG has excellent thermal characteristics. If the equivalent tem-perature on a height of 29.5” (75 cm) is considered representative of the comfort impression of a seated person, the following conclusions can be made:

• Not heated IQG (air filled) has a U-value of 0.176 Btu/hr f t 2 ℉ (1.0 Watt/m2K), which has a better result than a triple pane unit, and can be compared to a double pane unit filled with insulating gas.

• IQG has several positive consequences:

• A small vertical temperature gradient: homogeneous air temperature spreading in vertical direction• Glass surface temperatures from 78.8 ℉ to 87.8 ℉ (26 ℃ to 31 ℃), completely eliminating the ‘cold effect’ of

the window• The possibility to adjust a lower air temperature in order to obtain the same equivalent temperature

• Heat losses towards the outside are very small: the outside of a heating window is 2.1 ℉ (1.2 ℃) warmer than the outside of an identical, but non-heating window, for an outside temperature of 10.4 ℉ (-12 ℃).


33

• The temperature gradient of the glass is significantly smaller with IQG than with traditional heating systems. The IQG window forms the best ‘cold shield’. The consequence is a more constant air temperature in the room, which increases the comfort sensation.

• Due the radiant heat effects of IQG, a lower room temperature can be sufficient to reach the same level of com-fort feeling.

• During a normal heating season, IQG can produce energy savings of 25 %, compared to a convection heating system.


34

iqg heating glassiqglass.com/images/downloads/iqg_insights.pdfiqg heating glass insights ... found...

Documents