Historic Windows


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  • Research on building energy use and benefits of keeping historic windows versus replacing historic windows with high performance replacement windows.
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  • Recent research has shown that a window rehabilitation in conjunction with additional strategies that keep the historic window have energy savings in the range of a new high performance window.
  • Purpose of this conference is to see where preservation and sustainability are in agreement and where they are mutually beneficial.The share common goals to reduce environmental impact from the built environment without compromising future generations. Preservations want to make sure there is a future for the history of the past.To be considered for the national register of historic places buildings must be over 50 years old or otherwise significant. (Local example: Rothko Chapel, 1971).Buildings over 50 years old “historic” followed passive cooling strategies in the gulf coast’s humid environment out of necessity. These strategies can be emphasized and reactivated to reduce building energy use and improve occupant comfort.
  • Road blocks to the union of sustainability and preservation for windows.Myths promoted by high performance window manufacturers. Industry promotes myths to sell new windows with “warranties”. A warranty gives you an expected lifespan.Myths promoted by lack of information to the consumer.Preservationists rely on commonly held construction beliefs with often no little scientific proof. Beliefs often based on generational building knowledge being passed down.
  • Historic windows were dependent on passive cooling strategies and natural day lighting = high window/wall ratio
  • Changing the profile of the windows significantly changes the exterior appearance of the building. Often a defining feature.MFA-window significant feature of building’s designJefferson – Lower steel windows replaced in the 1980 with aluminum windows that have failed and had to be replaced.
  • At Houston’s latitude 80% of a building’s heat gain is primarily on the roofLeaving 20% for the walls. And with a 1:3 opening-to-wall ratio, a mere 5% heat gain is attributable to the windows.Department of Energy: 40-60% HVAC energy commercial and residential buildings.Cooling accounts for 15% of electricity use.
  • HVAC system upgrades: High return on investment Adding Wall insulation can be more difficult depending on the substrate.
  • This example puts the embodied energy and carbon in existing construction and materials into context: A 50,000 sf commercial bldg = 80 billion Btu’s energy = 640,000 gal. gasoline @ $3.75/gal. = $2,400,000 = $48/sf If an equivalent new building would cost $200/sf, the existing building would be 25% more economical to renovate.
  • Assumes basic repair of the existing window.Assumes that HVAC equipment has not been replaced
  • Pleated shades applied to the inside of the window to improve thermal performance.Thermal improvement from the interior capillaries of the shades. It creates a thermal break from the interior and the exterior. Effectiveness of shades is dependent on the operator deploying the shades.Less thermally effective alternatives more appropriate for historic interiors include plantation shutters, venetian blinds.
  • Self adhesive clear film applied to the interior of the window glass. Started as car tinting film. Can reduce solar heat gain by 70% Reduces UV fading of fabrics, floors.Minimal exterior change. Low reflectivity. Allowed by THC. You want visual light transmission to be 70% or greater.
  • Replacement window Frame: Wood, metal (thermally broken, fiberglass, vinyl, polycarbonateGlazing: Double or triple insulated glass (not effective for hot/humid climate). Low-e coatingBright green mold growth within insulated glass
  • 1. Performance of one or more retrofit options studied was in the expected range of the new energy efficient window.2. Window replacement is the most costly solution requiring on average $30,000.
  • The combination of exterior storm panel and cellular shades or interior window panel achieved energy savings in the range of the high performance window
  • Difference of only $29/ year from high performance window and retrofit option.Energy impact is much lower if HVAC has already been upgraded because less energy is being used to heat and cool. HVAC replacement will give you more energy impact than window upgrades.
  • Energy savings from cellular shade + exterior storm window is only slightly less than a replacement window.
  • Adjusted for regional material and labor costs. Assumes highest quality product. Lower quality = less expensive products also available.Cost of window replacement includes costs for interior repairs (sheetrock, painting) and exterior siding repairs.Replacement most costly: Window replacement is the most costly solution requiring on average $30,000.Exterior storm + insulating shade:$15,000Exterior storm or interior storm: $12,000 per homeInsulating shades: $3,000.
  • Common types of historic windows in the Gulf Coast Region that retrofitted their windows instead of replacement.Fort Bend: sister courthouse in Hays County Courthouse in San MarcusJefferson: Million Dollar CourthouseLavish interiors
  • Window submittal
  • Every window is different, even within the same building
  • Insulated glass is acceptable if it can fit within the existing frame.Every window is differentLook for unsound metal
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  • Historic Windows

    1. 1. Historic Windows: Don't replace, retrofit for energy savings Gulf Coast Green 2013 May 2, 2013 Session 3 Alexis McKinney AIA, LEED BD+C Bailey Architects alexism@baileyarchitects.com
    2. 2. “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.
    3. 3. 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.
    4. 4. 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
    5. 5. Preservation = Sustainability Preservation V. Sustainability rather than
    6. 6. 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
    7. 7. 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
    8. 8. Windows Critical to Character • Dominant visual element of the building exterior. Jefferson County Courthouse, 1932 MFAH, 1953, 1974
    9. 9. 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
    10. 10. 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
    11. 11. 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
    12. 12. • 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
    13. 13. • 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
    14. 14. 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
    15. 15. 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
    16. 16. 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
    17. 17. 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
    18. 18. 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
    19. 19. 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
    20. 20. Retrofit options achieve performance in the same range of new windows in all climate types. Findings:
    21. 21. 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:
    22. 22. Findings: Window replacement maximized average energy cost savings and CO2 savings but not by much. Energy Savings $29/yr NTHP
    23. 23. Findings: Window replacement maximized average energy cost savings and CO2 savings but not by much. CO2 Savings 734 lb/yr NTHP
    24. 24. 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
    25. 25. Common types of windows: Steel Local Example: Jefferson County Courthouse, Beaumont 1932 Art Moderne 14 stories Architect: Fred C. Stone & Augustin Babin 1909 Neo-classical, “Texas Renaisance” 3 stories + dome Architect: C.H. Page Wood Local Example: Fort Bend County Courthouse, Richmond
    26. 26. 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
    27. 27. Components of wood windows: Wood Window Repair, Rehabilitation, and Replacement Exterior Interior
    28. 28. 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
    29. 29. Components of steel windows: • Gang operation controls & parts • Solid steel sash & frame • Glass tight in sash with flexible putty • Tight fitting sash lock • Weatherstripping
    30. 30. 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.
    31. 31. • 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
    32. 32. • 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
    33. 33. 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.
    34. 34. Alexis McKinney AIA, LEED BD+C Bailey Architects alexism@baileyarchitects.com This concludes The American Institute of Architects Continuing Education Systems Course Thank you for your time Any Questions??