ENVELOPE
What's an envelope? In this case, it's your home's protective shell--made up of the walls, windows, doors and roof. How well your home's envelope performs greatly affects energy efficiency. Air that leaks out of a home through the envelope results in higher energy consumption and energy costs. Spending money to improve the building's envelope will not only reduce energy use and costs but increase comfort.
Windows...Windows allow the transfer of heat and are typically the most vulnerable part of your structure's envelope.
Double hung, single hung and horizontal sliding windows are especially prone to leaks since they must slide in order to operate creating a poor seal. During the heating season, when windows will remain closed use temporary or reusable putty caulk to seal gaps. It can be removed at winter's end.
Single-pane windows have very little insulating value. Double- and triple-pane windows provide much higher insulating value because the extra glass and air space resist heat flow.
Aluminum window frames causes conductive heat loss and are prone to condensation.
If your windows are older and not energy efficient, reduce heat loss through windows in the following ways:
- As soon as the sun goes down, go through the house and close shades and curtains.
- During the day, open all the shades and curtains, except those on north-facing windows, to take advantage of solar heat gain.
- Install seasonal storm windows. Storm windows can reduce your heat loss through the windows by 25% to 50%.…to reduce heat gain through inefficient windows:
- Install exterior-mounted sunscreens at South and West-facing windows.
- Plant seasonal shade trees on the South and West sides of the house.
- Install awnings or overhangs outside at South and West-facing windows. The awnings should be deep enough to shade windows from the high summer sun, but not so deep as to shade the windows from the lower winter sun.Installing treatments like shades or curtains will increase the R-value (insulating value) of windows when treatments are closed, reducing heat gain or loss.
Arrange furnture to take advantage of cross breezes from open windows.
Apply caulk to all joints in the window frame and the joint between the frame and the wall as a general precaution against leaks.
At night, turn off AC units and open up windows to let cool air in. In the morning, close all windows to trap cool air inside.
Doors...Very few doors shut perfectly with no air gaps. Several products are available from hardware stores to fill gaps of variable sizes.
Apply caulk to all joints between the door frame and the wall to stop leaks.
If you can see light or feel air through the joints between the door and its frame, install weather stripping to fill the gap.
Gaps between the door and the floor can be elminated either with floor mounted theshholds or door-mounted gaskets or sweeps.
Insulation...If you are unsure of what insulation you have, a qualified home energy auditor can identify the amount of insulation you have and need.
Here are some general guidelines for insulating your homes envelope:
R-value recommendations:
- Attic, 38
- Exterior wood frame wall cavity, 13 or 15 if 2x4 wall, 21 if 2x6 wall
- Floor, 25 (Over unheated, uninsulated space)
- Crawl space wall, 19 (Crawl space walls are only insulated if the crawl space is unvented and the floor above the crawl space is uninsulated.)
- Basement wall, 11Types of insulation:
- Cellulose-blow-in made from recycled paper
- Cotton batting made from recycled denim
- Formaldehyde-free fiberglass
- Recycled-content fiberglass
Penetrations
Fill gaps around plumbing and other penetrations in your ceilings, walls and floors.
Keep your fireplace damper closed when not it use to reduce home heat loss.
Exterior
Shade trees, window awnings and exterior solar shades can all help to minimize your homes solar heat gain on hot days.
Thermal Performance Resources
ENERGY AUDITS
To find an energy inspector. Look under Energy Management and Conservation Consultants in the phone book or go to homeenergytuneup.com or call 888-203-5262
WINDOWS
energystar.gov Find energy efficient windows
Insolroll Window shading products made in Colorado
North
Solar Screen Custom transparent solar shades
INSULATION
bondedlogic.com Natural fiber insulation products such as UltraTouch, recycled denim insulation
guardianfbp.com Guardian Fiberglass Insultaion contains 30% post consumer recycled glass and 5% post industrial recycled glass
jm.com Johns Manville Formaldehyde-free fiberglass Insulation
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