Caulk Windows to Save Convective Heat & Cooling Loss for Passive Solar Heating & Cooling

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Conserving Energy: Stop Conductive Loss (keeping the indoor air in and the outdoor air out)

By working to eliminating infiltration of outdoor air you can contribute enormously to heating or/or cooling savings in a building. The loss of conditioned air through cracks and leaks in a building can easily account for as much as 50% of the total heating or cooling loss in that building. You need to take a very careful look at the construction of a home to find all of the places that air is leaking into and out of the building. Leaks around windows and doors can contribute very considerably to heating or cooling losses through the mechanism of infiltration in the building. For example a 1/8 inch space around a door is the same as a six inch diameter hole right through the wall. Less obvious sources of infiltration heating and cooling losses include air movement through:

  • Porous building materials such as brick, wood, cinderblock, plaster and wallboard
  • The thermosiphoning of air up the furnace flue when the furnace is not running
  • The drier vent
  • The mail opening or chute
  • The openings of exterior doors
  • Hairline cracks around ceilings, floors, and in corners of rooms
  • Holes in walls where utility lines (gas, water, telephone, electrical conduit) lines enter
  • Holes in walls and ceilings where light fixtures, exhaust fans and vent pipes are installed
  • Wall electrical outlet and switch cover plates
  • Attic Door or hatch seals
  • Outdoor faucet fixtures
  • TV antenna entry line
  • Utility meters which are mounted on exterior walls
  • Wall or ceiling air conditioning unit seals
  • Chimney penetrations of walls and ceilings
  • Exterior joints such as where a porch or steps connect to the house
  • Cracks in the foundation
  • Openings around inset cabinets such as bathroom cabinets
  • The junction where the storm windows meet window frames
  • The junction where double-hung sash windows meet

Caulking Those Cracks

The gaps and cracks in both the inner and the outer shell of a house need to be sealed if convective heating or cooling losses are to be eliminated. Around the house, where ever two different materials come together, air leaks are likely. You can test for leaks in these places by moving a candle along the questionable seam.

A house in a cold climate can loose up to 50 % of its heat simply through leaks around door and window frames and at construction joints. The added benefit of caulking air leaks is that water leaks at the same location are subsequently prevented. This can save much money and effort in future since water leaks eventually lead to the need for repairs.

When caulking air leaks on the exterior of a house check the following areas:

  • Where the siding meets the trim
  • Where the siding meets the foundation
  • Where the siding meets the chimney
  • Where electrical outlets, gas and water lines enter the house
  • Door frames
  • Window frames

When caulking air leaks on the interior of a house check the following areas:

  • Where pipes, wires or light fixtures penetrate the ceiling or walls
  • Where the furnace flue goes through the ceiling or roof or un-heated basement
  • Where edges of the attic floor and exterior walls meet
  • Where the ceiling panels and the interior walls and frames meet

Caulking needs to be carried out in the spring or in the fall. Caulk does not perform well if it is applied at temperatures that are either too hot or too cold. Large cracks will need the application of expanding foam. Expanding foam tends to bubble out as it dries. But, once it is hardened it can be shaved back with a knife.

Caulking a house can make an enormous difference to the amount of energy consumed in heating or cooling the house. The principal of “first stop the bleeding” is definitely at play here. A lot of energy can be just drifting away through the various spaces in the shell of the house. There is not a lot of point in adding any type of passive heating or cooling system (or any other energy improved heating or cooling system) to a house before of these losses have been taken care of.


Anderson, Bruce and Malcolm Wells.(1994) Passive Solar Energy Second Edition, The Homeowner’s Guide to Natural heating and Cooling. Brick House Publishing Company, Amherst, New Hampshire,

Bossong, Ken and Jan Pilarski.(1982) Passive Solar Retrofit for Homeowners and Apartment Dwellers. Citizens’ Energy Project, Wash D.C. report series no.137" Home owner’s Guide to Passive Solar: An Overview"

This post is part of the series: Passive Heating and Cooling

Passive Heating and Cooling Technology uses the natural movement of energies in and around a building to heat and cool the building. By using the principals of passive heating and cooling you can economically eliminate most of the external energy that is required to heat or cool that building.

  1. Passive Heating And Cooling
  2. How Does a Passive Solar Heating System Work? Direct, Indirect & Isolated Gain
  3. Home Energy Conservation: Step One to Passive Solar
  4. Save Your Heating and Cooling Energy by Controling Convective Heat Loss and Cooling Losses
  5. Window Weather Stripping for Your Passive Solar House
  6. Door Weather Stripping for Energy Conservation
  7. Save Your Heating and Cooling Energy by Controling Conductive Energy Losses