Historic Windows: Don't replace, retrofit for energy savings

Gulf Coast Green 2013May 2, 2013 Session 3Alexis McKinney AIA, LEED BD+CBailey Architectsalexism@baileyarchitects.com

“Gulf Coast Green” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Course Description

While windows can be a low performer on a historic building they are not the lowest hanging fruit when improving the building’s energy performance. Once larger issues such as sealing ductwork, adding insulation, and upgrading the HVAC system are complete windows can contribute to measurable energy savings. Recent studies have documented energy savings from window retrofits when compared to high performance window replacement. The retrofit options studied in five different climates include weatherstripping, exterior storm window, interior window panel, insulating cellular shade, combination of exterior storm window and cellular shade, interior surface film, and a new high performance replacement window. Historic windows are highly durable using old growth or higher quality materials, easily repairable, reduce waste and avoid production of materials for new windows.

At the end of this program, participants will be able to:

1. Describe the positives and negatives of different historic window retrofit options for the gulf coast region.

2. Compare the return on investment of window retrofit versus high performance window replacement.

3. Understand the benefits of retaining historic windows during a building renovation.

4. Understand the components in wood and steel windows and the strategies available to maximize energy savings.

Learning Objectives

Preservation = Sustainability

Preservation V. Sustainability

rather than

Common Window Myths• A new window is better than an old window.• Old windows are bad for building performance.• High performance windows have quick energy payback

because they are energy efficient.• Old windows cannot be easily fixed and are expensive.

Bust the Myths!• Avoid common Preservation beliefs• Use science based proof• NO generalities

Windows Provide:• Maintains historic character• Occupant control – operable• Passive ventilation• Fresh air – operable, screens• Sun shading – awnings• Natural day lighting• Occupant views • Glare control• Privacy

Jefferson County Courthouse, 1932Camp Mabry Bldg 1, 1918

Windows Critical to Character• Dominant visual element of the

building exterior.

Jefferson County Courthouse, 1932

MFAH, 1953, 1974

National Park Service considers windows significant to a building if:

After

Windows Critical to Character

• Original to the building• Are of the original design

intent• Are of the period style or

building type• Are from period of significant

change to the building• Examples of exceptional

design or craftsmanship

Before

U.S. Energy Information Administration

• HVAC costs account for 40% - 60% of residential and commercial energy use.

• 10% of air loss is due to windows in a typical American home..

• Other components contributing to energy costs in commercial and residential buildings• Under-insulated walls and roofs, • Un-insulated wall and roof penetrations, • Doors (air infiltration)• Foundations• Air leaks at any opening• Un-insulated ducts

Energy Use

Select Low Hanging Fruit First

Low rise buildings, 1-3 floors, receive 80% of their heat gain on the roof.

Roof and floor insulation upgrades offer the biggest return on investment.

Consider other energy efficient options first before windows:• Air sealing• Improving the efficiency of the HVAC system

Insulate

Roof & crawl space insulation

• New windows consume 2-3 BTUs from production. Energy payback can be 40 years and up.

• Manufacture new materials, maybe not be recyclable (vinyl)

• Construction waste fills landfills

Embodied Energy

• Compared residential retrofit strategies in 5 climate zones for cost, energy, and carbon savings.

Preservation Green Lab & Cascadia Green Building Council; 2012

Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit and Replacement

• Studied Strategies– Weather stripping– Exterior storm window– Insulated cellular shade– Exterior storm window & insulating

cellular shade– Interior surface film (used on exterior

in hot climate)– New, high performance replacement

window

Pros• Improves air tightness around the sash. • Inexpensive materials: Spring metal,

compressible tape, sealant bead, or felt.• Easily installed by homeowner.

Cons• Requires regular maintenance• Must be continuous

Fort Bend County Courthouse

Weatherstripping

Pros• Exterior applied window unit for

improved energy performance & storm protection.

• fixed or operable with screen.• Improves energy performance,

extends the life of the historic window.

• Blocks noise infiltration.

Cons• Changes exterior window

appearance.• Drainage maintenance.

NTHP

Exterior Storm Window

Pros• Improves thermal performance.• Not visible from exterior.• Easier to install than exterior panel.• Glass or plastic with UV prevention.

Cons• Mostly fixed panels not allowing

access to window or ventilation.• Can reduce visibility• Condensation issues!

Montpelier Mansion

Interior Storm Panel

Pros• Improved thermal performance• Daylight control & privacy• No change to historic window• Common interior appearance• Manual, motorized, wireless options• More layers of cells = more efficient

Cons• Dependent on operator• Can reduce visibility and day lighting

Bob Vila

Insulating Cellular Shades

Pros• Reduces solar heat gain• Reduces UV by 99%. Prevents fading• No change to historic window• Prevents shattering of impacted glass• Applied to existing glass• Maintenance free• Low-e coating can be applied to

existing glass

Cons• Film can appear reflective or reduce

light transmission at higher levels• Reduces winter solar heat gain

Solutions.com

Interior Surface Film

Pros• Predictable performance; tested• Easily specified and calculated for

energy modeling.• Warranty

Cons• Changes appearance of window• Cannot be repaired in the future• Expensive• Removes original material from

building• Limited lifespan

High Performance Window

Retrofit options achieve performance in the same range of new windows in all climate types.

Findings:

NTHP

Exterior storm window and cellular shades or an interior window panel achieved the same annual energy savings as a high performance window in Atlanta (hot, humid climate).

Findings:

Findings:Window replacement maximized average energy cost savings and CO2 savings

but not by much.

Energy Savings $29/yr

NTHP

Findings:Window replacement maximized average energy cost savings and CO2 savings

but not by much.

CO2 Savings 734 lb/yr

NTHP

Findings: Return on Investment• Most retrofit options had a better return

on investment than window replacement.

• Insulating cellular shades had highest ROI of 5.2%

• Replacement windows ROI of 1.8%

• If weatherstripping and window film are installed by the homeowner the ROI is 20 – 30%

NTHP

Common types of windows:SteelLocal Example:Jefferson County Courthouse, Beaumont

1932 Art Moderne14 storiesArchitect: Fred C. Stone & Augustin Babin

1909 Neo-classical, “Texas Renaisance”3 stories + domeArchitect: C.H. Page

WoodLocal Example:Fort Bend County Courthouse, Richmond

Components of wood windows:• Tight joints• Glass tight in sash with flexible putty• Weatherstriping between sash and

frame forming seal• Correctly sized sash weights• Sash cord• Hardware: sash lock & handle

All components necessary for a functioning window

Components of wood windows:

Wood Window Repair, Rehabilitation, and Replacement

Exterior Interior

Steps to repair wood:• Evaluate the condition interior and exterior

(signs of water damage, termites, unsound wood)

• Remove paint• Remove & repair sashes. Repair glazing putty.

Protect the glazing.• Repair the frame & sill while sash is removed.

Install new sash cords.• Install weatherstripping (sash & frame).• Repaint.Final condition should be “sound”. The goal is not perfection

Components of steel windows:• Gang operation controls & parts• Solid steel sash & frame• Glass tight in sash with flexible putty• Tight fitting sash lock• Weatherstripping

Steps to repair steel:• Remove paint• Replace severely corroded parts. Repair

minor corrosion • Apply high performance coating or new finish• Reglaze sashes with flexible putty• Install weatherstripping• Adjust existing or new hinges, locks,

operating arms and latches or operation.

• Get blower-door test. Discover where air is leaking. Fix the problem.

• Install insulation• Replace HVAC system• Repair existing windows• Install cellular shades and

weatherstripping• Save money• Install exterior or interior storm

windows• Conduct routine maintenance

Avoid

Save the existing windows= Save energy

• Historic windows can be repaired by non-technical skilled labor (homeowner or facilities).

• Unlimited lifespan. • Prevents construction materials filling

landfills. • Avoids production of new materials.

Save the existing windows= Save energy

Resources

Saving Windows, Saving Money Evaluating the Energy Performance of Window Retrofit and Replacement. Preservation Green Lab; 2012.

Technical Preservation Guidelines: Upgrading Historic Building windows. Caroline Anderson, U.S. General Services Administration, April 2009.

The Repair of Historic Wooden Windows. John H. Myers, National Park Service Preservation Brief 9, 1981.

The Repair and Thermal Upgrading of Historic Steel Windows. Sharon C. Park AIA, National Park Service Preservation Brief 13, 1984.

Measure Guideline: Wood Window Repair, Rehabilitation, and Replacement. U.S. Department of Energy; December 2012.

Windows: Energy Efficiency Facts and Myths. Shanon Perterson Wasielewski; 2004.

Alexis McKinney AIA, LEED BD+CBailey Architectsalexism@baileyarchitects.com

This concludes The American Institute of Architects Continuing Education Systems Course

Thank you for your time

Any Questions??