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Weatherization Guide

Weatherization Guide

Overview

ENERGY STAR Common Air LeaksReducing the amount of air that moves in and out of a building will provide two benefits. The first is that it will reduce heating and cooling costs, and the second is that it will improve indoor comfort. Usually, the best way to identify areas to be addressed is by starting with an in-home energy assessment (also known as an "energy audit"). These are done by professionals, which are sometimes available at no or low cost from local utility companies, resulting in a series of specific recommendations and next steps to cost effectively reduce energy use. The most comprehensive type of assessment will include a blower door test, using a high speed exhaust fan temporarily placed in a door opening to depressurize a building, allowing areas of leakage to be pinpointed and sealed. But, there is also a lot that a do-it-yourselfer can do independently.

To know where to start, identify the thermal envelope of the building, which is the barrier between the intended conditioned space (the occupied parts of the building that is heated or cooled), and the unconditioned space (the unoccupied parts of the building that are not heated or cooled). When finding and sealing air leaks, the priority should be to seal between the conditioned spaces and unconditioned spaces, such as around exterior walls, which is more important than sealing gaps on interior walls between two conditioned spaces.

A second key concept to take into account is the "stack effect". During cold winter days heated indoor air will rise, with conditioned air being pushed out through leaks near the top of a building, while unconditioned air from outdoors will be drawn into the building from leaks in the basement or crawlspace.  Conversely, on summer days, hot outside air will be drawn into an attic, with cooler indoor air exiting from leaks lower in the structure.  Thus, sealing between the top floor and the attic, and between the bottom floor and the crawl space or basement, will deliver the greatest benefit. 

Leaks Up High

Because many weatherization measures can be done by homeowners and renters, and because the products used are often relatively inexpensive, the payback on do-it-yourself air sealing is often seen in less than a year, which means the savings over the course of a year will exceed the cost of the measures installed. When also planning to add insulation, undertake weatherization and air sealing work first, because penetrations are far easier to access before insulation is in place.

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Efforts to reduce air leaks that contribute to high heating costs should begin in the attic, identifying penetrations between the conditioned space and the unconditioned space. Air leaks are most likely to be found...

  • around ducts that pass through the attic
  • chimney penetrations from the living space through the attic
  • penetrations for plumbing vent pipes
  • openings around the perimeter of an attic hatch or door
  • electrical junction and light fixture boxes
  • bathroom and wholes house fans
  • near the top of exterior wall framing

When inspecting for air leaks, especially if any insulation is to be disturbed, it is prudent to wear protective clothing, gloves, and a dust mask or HEPA respirator.

Leaks Down Low

The next most important area of focus would be eliminating infiltration/exfiltration from the unconditioned space under a house or building to/from the conditioned area. These air leaks are likely to be found around...

  • ducts that pass through the crawl space or basement
  • plumbing and furnace vent exhaust pipes
  • areas around water pipes leading to exterior faucets
  • the sill plate where the foundation and framing meet
  • openings around the perimeter of a basement door

As with work in an attic, in crawl spaces and unfinished basements, is always a good idea to wear protective clothing, gloves, and a dust mask or HEPA respirator.

Leaks On the Sides

Finally, reducing leaks around the perimeter of a building have the potential to reduce drafts, especially on windy days, improving comfort. A variety of temporary measures (especially good for renters), as well as permanent measures that can deliver savings for years, are readily available. Dirty areas on perimeter walls and ceilings often point to where air infiltration may be occurring.  The obvious areas to weatherize include....

  • exterior doors and door frames
  • window sashes and frames
  • penetrations for service entrances (cable TV, electric, natural gas)
  • exhaust vent flashing
  • around window and through-wall air conditioners
  • electric wall outlets

Measure List

Following are some of the easiest do-it-yourself measures available. Some of these may be available through this Web Site, as well as through local hardware and big box stores. 

Product Where to Use Price Tier / Typical Cost* How to Use It
Attic Stair Cover Attics: Over pull-down attic hatches. High: < $200.00 (per cover) Attic stair covers are made of either rigid foam or a soft material sewn into a box share, and designed to be placed over a pull-down attic stair hatch, reducing air infiltration/exfiltration around the perimeter of the attic hatch. Multiple sizes are available, eliminating the need to have to modify the cover to fit most attic hatches. Recommended Tools: Caulk (optional).
Caulk (high temperature) General Use: Small gaps between stationary parts of a house near high-temperature surfaces.  Low: < $10.00 (10 oz tube)  High temperature caulk is applied using a standard caulk gun, squeezed through the tip of the tube of caulk. It's qualities allow it to be used to complete the seal of small gaps in unconditioned spaces between non-combustible materials such as aluminum flashing and chimney and furnace vent pipe penetrations. Caulk will not, however, adhere well to dust, dirt, or porous surfaces. Recommended Tools: Standard Caulk Gun.
Caulk (silicone) General Use: Small gaps between stationary parts of a house.  Low: < $7.00 (10 oz. tube) Caulk is applied using a standard caulk gun, squeezed through the tip of the tube of caulk to fill any small gaps where non-moveable house parts meet. Caulk will not, however, adhere well to dust, dirt, or porous surfaces. Clean surfaces before applying caulk. Recommended Tools: Standard Caulk Gun.
Door Kit Doors: The top and sides of exterior door frames. Moderate: < $30.00 (per kit) A door kit consists of three pieces, one that spans the top horizontal part of the door frame, plus two longer pieces for the two vertical sides of the door frame. The carriers are made of wood, aluminum, or vinyl, with a soft rubber flange designed to press against the door when closed. Door kits are usually attached to the door frame with screws, positioned so that when the door is closed, the flange will press against the door, reducing drafts. Recommended Tools: Measuring Tape, Screwdriver, and a Saw/Hacksaw (if the kit needs to be cut to fit).
Door Sweep (automatic) Doors: The bottom of exterior doors for which the door will pass over a rug or carpet when opened. Moderate: < $15.00 (per sweep) Automatic door sweeps have a length (typically 36") equal to the width of most exterior doors, with a carrier made of aluminum, and a soft vinyl or rubber flange beneath the carrier. This type of door sweep is attached to the exterior of a door with screws, positioned so that when the door is closed, the flange will touch a stop on the door frame to press the flange down onto the threshold, reducing drafts from underneath the door. When opened, the flange will automatically rise to clear and rugs or carpets the door will pass over. Recommended Tools: Measuring Tape, Screwdriver (a saw is not usually used because it is particularly difficult to cut an automatic sweep to fit narrow doors).
Door Sweep (fixed) Doors: The bottom of exterior doors for which the door will pass over a smooth floor when opened. Low: < $10.00 (per sweep) Fixed door sweeps have a length (typically 36") equal to the width of most exterior doors, with a carrier made of plastic or aluminum, and a soft vinyl or rubber flange beneath the carrier. Most metal door sweeps are often attached to the door with screws (some plastic sweeps use an adhesive strip to allow the sweep to be affixed to a door without screws), positioned so that the flange touches the threshold when the door is closed, reducing drafts from underneath the door. Standard sweeps are best used in rooms in which the floor the sweep will pass over when the door is open is hardwood, tile, or a solid surface, rather than rugs or carpets. Recommended Tools: Measuring Tape, Screwdriver (for sweeps with screws), Hacksaw (for metal sweeps when used on doors less than 36" wide)
Foam Switch/Outlet Gaskets Electrical: Behind electric outlet and switch plates on exterior walls. Low: < $0.12 (per gasket) Foam gaskets are easily installed behind electric switch and outlet cover plates. Cover plates are held in place with one or two screws, so to install unscrew the cover plate, place the gasket behind the plate, and reinstall. In multigang applications, to resize the gasket it may be trimmed with scissors or a utility knife. Recommended Tools: Screwdriver, Scissors or Utility Knife (for multi-gang applications).
Foam (low expansion gun foam) General Use: Around plumbing vent pipes, bathroom and wholesale house fan housings, between studs and framing, and around the exterior of electrical boxes. Moderate: < $20.00 (24 oz. can) Low expansion gun foam is dispensed using a foam applicator gun. Use of a foam applicator gun allows for more precise control, and one gun can be used for multiple cans of foam. Cans usually hold 24 ounces of foam. Once sprayed, it will expand to seal the exposed gap, and dry in place. Recommended Tools: Foam Applicator Gun.
Foam (low expansion straw foam) General Use: Around plumbing vent pipes, bathroom and whole-house fan housings, between studs and framing, and around the exterior of electrical boxes. Low: < $10.00 (24 oz. can) Low expansion straw foam is dispensed directly from the can. Cans usually hold 12 ounces of foam. Once sprayed, it will expand to seal the exposed gap, and dry in place. Recommended Tools: None.
Mastic Ducts: Heating/cooling/ventilation ducts in unconditioned spaces. Moderate: < $35.00 (1 gal. bucket) Mastic is a latex compound that can applied over sheet metal gaps in ductwork with a trowel (or by hand if one is wearing disposable gloves), preventing the surrounding air in unconditioned parts of the building from being drawn into the conditioned areas of the building through the ducts. Sealing ducts also serves to prevent heated or cooled air flowing throughthe ducts from escaping into unconditioned spaces. It can be reinforced or can span larger gaps by using mesh tape designed for use with Mastic. Recommended Tools: Trowel and/or Latex Gloves.
Plastic Interior Storm Windows Windows: Across the face of windows that do not need to be opened.  Low: < $3.00 (per window) Plastic interior storm windows consist of sheets of clear plastic that can be stretched taut across the interior face of a window to eliminate drafts. While plastic interior storm windows can be left in place for a period of time, it is generally intended to be a temporary measure, removed at the end of the heating season. Typical sizes include 38 inches by 64 inches and 42 inches by 62 inches. The plastic can be trimmed to fit smaller windows. Recommended Tools: Scissors.
Recessed Can Cover Electrical: Over recessed can fixtures that penetrate into an uncodtioned attic space.  Moderate: < $40.00 (per cover) Recessed can covers are designed to be placed on top of recessed light fixtures that penetrate into an unconditioned attic space, reducing air infitration/exfiltration between the conditioned living space and the unconditioned space. Recommended Tools: Caulk (optional).
Rope Caulk Windows: Around window sashes that will not be opened. Low: < $5.00 (30' roll) Rope caulk is pliable caulk that can be pressed into place with fingers, sealing small gaps, such as the crack between a window frame and a window sash. While it can be left in place for a period of time, it is generally a temporary caulk, making it especially suitable for use by renters in apartments. Recommended Tools: None.
Window/Door Weatherstripping (rubber) Windows/Doors: On a door jamb or window frame. Low: < $9.00 (10' roll) This type of rubber weatherstripping remains pliable in extreme temperatures, ranging from - 40 degrees Fahrenheit to 140 degrees Fahrenheit. It has an adhesive backing, allowing it to be attached to a door jamb or to a window under the lower or upper sash of a double hung window, so when the door or window sash presses against the foam it compresses, a tight seal is created. This type of weatherstripping is sold in 17 foot long rolls, in thicknesses of 1/8th inch, 5/16th inch, and 7/32nd inch. Always clean the surface well before installing to ensure good adhesion.  Recommended Tools: Measuring Tape, Scissors.
Window/Door Weatherstripping (foam tape) Windows/Doors: On a door jamb or window frame. Moderate: < $3.00 (17' roll) This is easy-to-install open-cell foam tape with an adhesive back that can be attached to a door jamb or to a window under the lower or upper sash of a double hung window, so when the door or window sash presses against the foam it compresses, a tight seal is created. This weatherstripping typically comes in a 17 foot long roll, able to seal a gap up to 3/8ths of an inch. Always clean the surface well before installing to ensure good adhesion. Recommended Tools: Measuring Tape, Scissors.
Window/Door Weatherstripping (vinyl) Windows/Doors: Attaches to a door or window frame. Low: < $5.00 (17' roll) V-Strip is made of soft vinyl that either comes in 7 foot lengths molded in a "V" shape, or in a pre-scored roll for which the plastic can be folded into a "V" shape by the user. One half of the "V" will have an adhesive, allowing it to be attached to a door or window frame sealing the gap, while allowing the door or window to be still be open and closed normally. When installing, the open end of the "V" should point outward. Always clean the surface well before installing to ensure good adhesion. Recommended Tools: Measuring Tape, Scissors.

* Actual prices will vary

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Other Considerations

Common sense practices can also make a big difference, such as closing keeping windows and door closed when the heating or air conditioning systems are running, closing fireplace and wood stove flues when the fireplace or stove is not in use, and turning off kitchen and bathroom exhaust fans once they are no longer needed. These can all help to reduce uncontrolled air infiltration and exfiltration.

While a blower door test undertaken by home performance professionals will most accurately find sources of uncontrolled infiltration, a non-professional can search for leaks by first closing all windows and doors and turning on kitchen and bathroom exhaust fans simultaneously, and then pass a damp hand (or a lit incense stick) near likely locations. Doing this on cold days is best.

With comprehensive air sealing complete, especially when done by a professional, buildings may require some amount of controlled ventilation to preserve indoor air quality and remove excess moisture. Products such as ENERGY STAR® certified heat and energy recovery ventilators can accomplish this while transferring the temperature of the conditioned air being exhausted to the incoming fresh air from outside. In general, ERVs and HRVs should exhaust air from kitchens and bathrooms, while introducing fresh air into bedrooms and living spaces. Some ENERGY STAR® certified bathroom exhaust fans also have a low cubic foot per minute (cfm) speed to support continuous exhaust without the need for additional ventilation ductwork.

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Additional Resources

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Disclaimer: The content presented on this page was prepared by the individual(s) listed below, and does not necessarily refect the views of the company or companies utilizing this site.

Contributor: Philip Scarbro

© 2024, AM Conservation, All Rights Reserved.

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