bs fundamentals by john ring

8/7/2019 BS Fundamentals by John Ring

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Fundamentals of

Building Science

Presented by John H. RingEnergy Wise Solutions, Inc.

Knowledge for Building Rightin the 21st Century



Learn what Building Science is and why we

need to understand it

Understand the basic physical principals of Building Science

Be prepared to apply those principals to real

life building

Copyright Energy Wise Solutions, Inc. 2

Course Objectives



It is the study of the interaction between Occupants

Building Components & Systems

Environment

Focusing on the flows through the buildingenclosure of Heat

Air Moisture


What is Building Science?



We no longer accept indoor environmental

conditions that we used to tolerate

We demand more control of our indoor environment

We have a limited supply of energy for

which demand & costs continue toincrease, so we must consider energy

conservation


Building requirements

have changed



Tighter building assemblies

More thermal insulation

More power vented furnaces & heaters

Air conditioning with flexible air ductdistribution systems

A multitude of new products to deal with Often combined in new ways


How do we build differently today

than we did even 30 years ago?



Unsafe conditions

Unhealthy conditions

People are uncomfortable

Energy is wasted

Materials are wasted

Increased operating costs Failure of components or systems

We damage the environment


What happens when buildings

don¶t work?



A building creates an interior

environment that is different from the

exterior environment ± it is anEnvironmental Separator

Its function is to separate the inside

from the outside as required by the local environment

according to the wishes of its occupants


Think of a House as

Your Environmental Separator



A building provides shelter From the elements

From other dangers

The interior environment should be

controllable by the occupants in a

manner their meets their needs





The Building System ±

Functional Relationships



Studies the interaction of all of

these functional relationships

It tells us how buildings actuallywork

It tells us how to design, build,

operate, diagnose, and fix them


Building Science



Provide strength and rigidity

Control rain, wind & ground water

Control fire Control heat flow, air flow, and

moisture flow

Control contaminants, environmentalhazards and odors, insects, rodentsand critters


We ask a Building to do

ManyT

hings



Control light and solar radiation

Limit noise and vibration

Provide comfort

Be durable

Be economical to purchase and

operate

Be aesthetically pleasing




SAFE

HEALTHY

COMFORTABLE

DURABLE

ENERGY EFFIC

IENT

ENVIRONMENTALLY FRIENDLY


The Goal of Building Science

is to Provide a Home that is



Building Science is the study of

Heat Flow

Air Flow

Moisture Flow

through the building enclosure


Let¶s Review



Not all these forces are equal

All are important, but some more than

others In buildings, aside from safety, control of

HEAT

AIR

MOISTURE

stand above all other considerations




We have the bread on the outside ±we call that the Building Envelope ±

and the HAM on the inside

HEAT

AIR MOISTURE


An easy way to remember what Building Science is:

Think of a the House as a

HAM SANDWICH



THE LAWS OF PHYSICS

ALWAYS

WIN OVER OPINIONS


Building Science



Everything in a house interacts,

from the footing to the roof ± andall components and systems in

between CHANGING ONE PART OF THE

SYSTEM WILL AFFECT OTHER

PARTS OF THE SYSTEM


The House is a System



In the 1970s, in response to theenergy crisis ± yes, we did have one

in the past ± the levels of insulationwere substantially raised in homes. Also, following concepts transplantedfrom cold climates, houses in cooling

climates were sealed tighter andplastic was wrapped over thatinsulation.


The House as a System



Yup, it did save energy and increased comfort, butthat plastic trapped a lot of moisture and many of those houses have had problems with mold andstructural rot.

These problems came about because of a lack of system thinking ± no one considered the effect on thehouse of the combination of all that added insulation,plastic and the other changes.

While a few recognized the reasons for the problems,

it is only in the past 8 years that even the buildingcode has begun to change to reflect the need for System Thinking.


The House as a System



If you build an airtight house (as youshould), and wrap it in a layer of insulation, the rest of the house willreact as our bodies do if we were towear a winter coat year round. Theairtight, insulated house will keep theconditioned air in, but it will also keep

moisture and pollutants in as well. Anyone who designs, builds or remodels must always be aware of this.





The House is an Interacting

System with People in the Middle

PeopleMechanicalSystems

Heat Lossand Gain

AirMovement

Moisture



Building Science strives to providehouses that are ±

SAFE ± HEALTHY ± COMFORT ABLE ±

DURABLE ± ENERGY EFFICIENT ±

ENVIRONMENT ALLY FRIENDLY

Of these, for most people, what issuedo you think is of primary importance?


Let¶s Review



COMFORT




³ that condition of mind in

which satisfaction isexpressed with the

thermal environment´1993 ASHRAE

Handbook of Fundamentals

Chapter 8


What isC

omfort?



Many homeowners complaints grow out of

comfort problems

COMFORT is the canary in the coal mine

What is causing the comfort problem may

also be causing problems with:

Safety & Health

Building durability Energy efficiency


Comfort Problems =

System Problems



Activity

Clothing

Temperature

Air Velocity

Moisture in the air (Rh) Radiant Surface Temperatures


Comfort Variables

Comfort complaints areexpressed in terms of airtemperature, but radiant

surface temperatures are usually the primary cause.



Now, let us discuss those things

that Building Science is all about

± the first is

HEAT FLOW




HEAT FLOWHeat flow is the movement of

heat from one surface to

another, or from one space to

another, through one or more

heat transfer mechanisms




Conduction

Convention

RadiationCopyright Energy Wise Solutions, Inc. 30

Methods of Heat Movement



The action of HOT moving to COOL

is always trying to take place by oneor more of these mechanisms.

The greater the temperature

differential, the stronger themovement.


Equi l ibri um is everything!



H OT COLD

=

WARM WARM


E verything in nat ure tries to

reac h a balanc e.



The transmission of heat

through matter withoutmotion of the conducting

body as a whole.


Conduction



Requires two solids to be in

contact with each other.


Conduction



Takes place within an object


Conduction



How do we control conductive

heat loss?

By slowing down the heat transfer with

InsulationThat is in contact with the surface

it is insulatingCopyright Energy Wise Solutions, Inc. 37

Conduction



The transfer of heat

when the motion of agas or fluid takes place


Convection



Is caused by: temperature differential

(natural)

mechanical action (forced).


Convection



Natural


Convection



Forced


Convection



ForcedYou run a ceiling fan or floor fan

to cool you

on a hot day.

H ow does

this w ork?


Convection



Natural convection works only by gravity;

that is, it works only up.

The warmer air, being lighter, rises.

Forced convection can work in any

direction:

It can work down as when the driving force ± a

ceiling fan, for example ± moves air down. It can work sideways, as with the fan in the

cartoon on the previous slide


Convection



Controlling Convection can only

be done with a

Barrier


Convection



The transfer of heat

through

empty space


Radiation




Radiation

Can

takeplace

in a

vacuum

Needsline of

sight



You go up into your attic to storesome items on a sunny day in

summer. The heat in the attic is

almost overwhelming. You get athermometer and find that thetemperature at the roof peak is

140º.W hat is happening?


Radiation



Radiation from the sun is heating the shingles.

The shingles, primarily through Conduction, heat

the roof sheathing below.

The hot sheathing, primarily through Radiation,heats solid surfaces below that are

within the line of sight of the roof sheathing.

Convection also plays a role in keeping the roof

peak hotter than the space below.


Radiation




Radiation



The previous example is illustrative of how a single

source of heat can result in all three heat flow

methods working at the same time to either cause

problems or do good.


Heat flow mechanisms



On a cold winter day you sit in your favorite

chair six feet from a single pane window and

don¶t feel comfortable

even with the ther-

mostat set at 78º.

H ow can this be so?


Heat flow mechanisms



Your body, and the clothing you have on,

are all at a higher temperature than the

window, and likely even the wall around it.

Your body heat moves by radiation to the

cold surfaces. You lose heat, making you

feel cool.


Radiation & Comfort



Because Radiation requires line of

sight to take place,

Blocking the Line of Sight

stops Radiation


Radiation




In Summary



The next part of our building

³HAM´ sandwich is

AIR FLOW




Air flow is the movement

of air - within a space

from one space to another


Air Flow



For air to flow into or out of a

building, or within two adjacent

inside spaces there must be

A hole and

A driving force


Air Flow in Buildings



Building Science is concerned withtwo types of holes that allow air movement into, out off, or within a

building: Designed - holes you pay for up front

Controlled by the occupants

Undesigned - these are free but cancost you a lot later

NOT occupant controlled





Designed holes are ± Ones we deliberately open & close

Doors and windows

Ones that are usually tightly dampered andopen only when needed

Kitchen exhaust fan vents

Dryer vents

Laundry room fans

Bathroom fans

Ventilation air-in systems





Air Flow in Buildings Undesigned holes -

Any wall penetration

Light fixtures

Switches & receptacles

Plumbing lines

Bottom and top plates

Rough openings

Boots in ceilings/floors

Fireplace inserts

In back of fireplace

inserts Exterior walls behind

tubs and showers

Attic entries

Under-eaves entries

Band joist areas

between floors

In-between floor chases Under door thresholds

Dropped soffits

Joist cavities under attic

kneewalls

Seams between rigidexterior sheathing

Ceiling height transitions




The best houses are those with

the fewest undesigned holes

It is not possible to eliminate allundesigned holes, but good

building practices will take care

of most of them





It used to be that little attention was paid

to building well sealed ± ³tight´ ±

houses. It was thought, and still is bymany, that a house needs to ³breath´,

and the numerous undesigned holes

allowed it to do that.





Today we know this is not true. We know

that all those undesigned holes decrease

comfort and increase energy costs.Today we understand that if the only

holes in the building envelope are the

ones we design, and the ³breathing´ is

deliberately controlled, the house willfunction much better.





Is this your house? Leaking all the air

you paid to condition!!



You have two choices:

1. Keep pouring in the conditioned air.

2. Plug the holes.



We now know, based upon SCIENCE, that we must:

BUILD TIGHT

&

VENTILATE RIGHT




Large undesigned holes must besealed first.

However, remember that smallholes add up. For example: an average 1/8´ gap

around an attic stairs hatch cover is

the same as a 4´ x 5´ hole in theceiling!





When air enters or leaves

a space it can be: Hot or Cold

Wet or Dry

Clean or Polluted

A combination of the above


Air Flow Fact



Air flow, in building science

terms, is measured in Cubic Feet per Minute (CFM) or

Cubic Feet per Hour (CFH)


Air Flow Fact



When we think of air pressure we used to

thinking in terms of Pounds per Square

Inch (PSI). However, within a building weare usually looking at very small pressure

differences. Those units are called:

PASCALS (Pa)


Air Flow Fact



A Pascal is about the amount of

pressure exerted by a pat of butter on

bread, or the weight of couple of stickynotes.

1 PSI = 6,894 Pascals

There are 220,600 Pascals of

pressure in an auto tire at 32 psi!


Air Flow Fact



Driving forces are: Heat (the chimney/stack effect)

Wind

Fans ± mechanical systems





One unit in = one unit out


Air Flow Rule 1

1 ft³ in

1 ft³ out

Air in the

house



Stack pressure is a function of

two things: T

he height of the building A 2-story house has twice the stack

pressure of a 1-story house

Temperature difference (

(T)indoors to outdoors


Stack effect (Heat)




Stack effect

NPP = Neutral Pressure Plane




Wind




Wind patterns



There are a lot of fans in the modernhouse. Some can cause seriousdepressurization of a house if make-upair is not provided. Bathrooms

Kitchen range hoods vented to the exterior

Downdraft exhaust cooktops

Clothes dryers

Central vacuums Whole house fans

Powered attic fans


Fans



The effect of fans is

cumulative and if several of

the major ones are on at thesame time the house can

really suck!

It adds up quickly!


Fans




Fans

150 CFM + 700 CFM + 50 CFM

= 900 CFM

Where is the make-up air coming from in a tightlybuilt house? In a 2250 ft² house this situation

would change all the air in the house in 30

minutes. Remember, 1 unit out ± 1 unit in!



Houses ± spaces ± with a positive

pressure in them BLOW

Houses ± spaces ± with a negativepressure in them SUCK

The major consistent cause of houses

that BLOW or SUCK is leaking ducts

outside the conditioned space


Fans - Mechanical Systems



If the dominant leakage is in the return

system, the house BLOWS


Fans - Mechanical Systems



What happens when a house, or a

portion of a house blows? Conditioned air is forced out of the house

replaced by unconditioned air resultingin:

Increased energy consumption

Decreased comfort Possible durability problems


Air flow



If the dominant leakage is in the output

system, the house SUCKS.


Mechanical Systems



What happens when a house, or a portion of

a house sucks? Unconditioned air is drawn in and conditioned

air is forced out resulting in: Potentially serious safety issues

Potential health problems if air is polluted

Possible durability problems

Increased energy consumption Decreased comfort


Air flow



Air, like water,

will tend to

move through

the nearest,largest

opening with

the least

amount of resistance.


Air Flow Rule 2

What if the window isnt the nearest,largest opening with the least resistance?



Air likes to be balanced. If there is a

pressure difference between two

spaces the air will move from the

area of high pressure

to the area of low

pressure to remove

the difference.


Air Flow Rule 3



Remember that air pressure isrelative. You cannot simply say

that a room has high pressure in it.

It must be³with reference to´

(WRT) another space. For

example: ³the master bedroom is

at a higher pressure than (WRT)

the adjacent hall.´




Heated air rises Cooled air falls


Air Flow Rule 4



In order for a house to perform properly

and efficiently there must be

a continuous Air Barrier surrounding the house. It provides one

part of what is known as the

Thermal Barrier


Air Barrier



The Building Envelope is

defined as those systems

and components thatseparate the interior

environment from the

exterior environment.


The Building Envelope



The Thermal Barrier

includes an unbroken Air

Barrier with a contiguous

layer of Insulation in

contact with it.


The Building Envelope




The Thermal Barrier



For air to flow into, out of, or

within a building it needs:

An opening A driving force:

Stack pressure

Wind Fans


Air Flow SUMMARY



Warm air rises, cool air falls

One unit of air in = one unit of air out

Air flows from high pressure to low

pressure

When trying to reach equilibrium, air seeks

the path of least resistance:

The nearest, largest opening with the leastamount of resistance


Air Flow SUMMARY



Now we move to the last part of our

³HAM´ sandwich:

MOISTURE

FLOWCopyright Energy Wise Solutions, Inc. 96



Moisture Flow has great

significance with regard to how a

house performs and functions asa system.

Most building performance

problems are caused bymoisture.


Moisture Flow



Moisture Flow

Affects: Health:

Mold Dust mites

Cockroaches

Bacteria

Durability &

Safety:

Wood decay

Corrosion

Termites




Moisture moves from

WET to DRYWhen materials get wet or they dry, it

is by moisture moving from the wetter

place to the dryer place in order to

achieve a balanced state.


Moisture Flow



There are four moisture

transport mechanisms:

Bulk Capillarity

Air Transported (Infiltration)

Vapor Diffusion


Moisture Flow



Moisture Flow

Bulk:

liquid water

(poor drainage,

water, roof,siding &

plumbing

leaks)




Moisture Flow

Capillarity:

wicking through

porous materials(concrete, wood,

brick, cellulose

insulation,

gypsum board)




Moisture Flow

Air Transportedor Infiltration:

whenever air moves,whatever is init moves with it,

including water vapor.




Moisture Flow

Vapor Diffusion: The movement of

moisture in mole-cular form from an

area of higher

vapor pressure to

lower vapor

pressure.


Moisture migratesto conditioned spaceby vapor diffusion.



Because we know that in a mixed humidclimate (most of NC) building materials and

walls often get wet, it is essential that they be

able to dry in both directions, usually by vapor

diffusion. Thus, except in very cold climates,the only place in a house where there should

be a vapor barrier is

under the slab

or on the crawl space floor.




Moisture Damage is caused by: Wet conditions (100% Rh) for a short time

Very high humidity (80%+) over a long time

Time Duration for damage depends on: The material affected

Temperature

The higher the temperature the more

accelerated the process


Moisture Damage



Three basic rules for deterring

moisture damage in absorbent

building materials: Keep the material dry!

Don¶t let the material get wet!!

Keep water away from the

material!!!


Moisture Damage



Moisture is transported four ways ± listed in

the order of wetting: Bulk Water Flow (liquid)

Capillarity (liquid) Air Transported (liquid or vapor)

Vapor Diffusion (vapor)

In terms of the HEALTH & DURABILITY of a

house, moisture control is of the greatestimportance.


Moisture Flow - SUMMARY



Everything we do in Green Building and

Remodeling should be based upon sound

Building Science principles. Without under-

standing these principles and how the house

works as a system we will not achieve the goal

of providing homes, schools and workplaces that

are Safe, Healthy, Comfortable, Durable, Energy

Efficient and Environmentally Friendly.

bs fundamentals by john ring

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