Straight Talk Articles

Your Basement Doesn’t Have to be a Money Pit
October, 2020

Dear Pat and Brad: 

I’ve heard a lot of the energy loss in a home comes from the basement. Is that true? If so, what can I do to make mine more efficient? – Andy

 

Dear Andy:

Yes, basements can use up to a large portion of your home’s energy(1), especially in colder climates. More importantly, basements are often key to improving energy efficiency throughout the house just as the under carriage of your car is key to its performance.   

 

Before taking action it’s critical to think about moisture in basements, a common problem.  Moisture can lead to mold, rot, and lowered effectiveness of insulation. As you make improvements in the basement you can solve moisture problems, or, if you’re unaware you could make them worse.   Look carefully for signs of water damage or moisture buildup such as rotting wood, mold, a stain on a wall or floor or just a musty smell.  Any untreated wood in contact with a cement floor or wall could be rotting.(2)  Search online for “test basement walls for moisture” and you’ll find a simple test you can do yourself.

 

You should also consider, before making improvements, whether radon or carbon monoxide could be a problem.  If you live in an area where radon has been a problem, get a radon test.  Carbon monoxide problems can be deadly.  If you have any type of combustion occurring in the basement, whether it’s a furnace, water heater or even a fireplace, make sure they have adequate ventilation and that you have working carbon monoxide detectors nearby.

 

An unfinished basement presents the most opportunities. If you have forced-air heating/cooling, the ductwork is probably leaky.  Sealing these leaks helps your system distribute air more efficiently and should make your house more comfortable.  The best way to seal ducts is with duct mastic.  Metallic tape is the next best solution.  Don’t use duct tape.(3) 

 

As you look at the ductwork, ask yourself if rooms throughout the house are heated unevenly in winter or cooled unevenly in summer.  If so, now is the time to bring in an HVAC professional. Sometimes minor modifications to the ductwork can make a big improvement in comfort. 

 

Next, seal all gaps, cracks and holes, especially where pipes and wires penetrate the walls or ceiling, including around the dryer vent.  Air often enters the home around the sill plate, which sits on top of the foundation.  If you can get to it, apply caulk.(4)  Seal any gaps and leaks around basement windows.  You may want to replace these windows, or install an egress window.

 

Insulation cuts energy use and improves comfort, but must be done correctly to prevent mold or exacerbate moisture problems.  The first area to insulate is the rim joist.  Rigid foam board can be carefully fitted between joists. 

 

Insulated walls make a room more comfortable.  If you’re building a new home there are advantages to insulating the outside of the foundation wall, but this is not a practical solution for most existing homes.  You can insulate the inside of the foundation wall if you’re sure moisture is not leaking through the wall from the outside.  Experts these days do not recommend fiberglass insulation in contact with the foundation.  Instead, they prefer sprayed-on foam or rigid foam board applied directly to the foundation wall.(5)  A wood framed wall can be butted up against the rigid foam and can be insulated with fiberglass or mineral wool batts.  The bottom plate of the wall, which sits on the concrete floor, should be pressure treated wood.(6)

 

Other ways to save energy in your basement include:

  • Insulate the hot water pipe coming out of your water heater;

  • Install LED light bulbs;

  • Replace the water heater, the washer or the dryer with an efficient new model.

 

As you can see, there’s a lot to making your basement more efficient and more comfortable.  We hope this information gets you moving in the right direction.

This column was co-written by Pat Keegan and Brad Thiessen of Collaborative Efficiency. For more information on basements and crawlspaces, go to the October 2020 More Information Page.

Footnotes

(1) https://www.energy.gov/articles/taking-scary-basements

(2) fixing basement moisture problems is a major topic all its own, with a variety of approaches.

(3) https://www2.lbl.gov/Science-Articles/Archive/duct-tape-HVAC.html

(4) For more info, see our August 2020 article on Sealing Air Leaks.

(5) www.ecohome.net/guides/2270/basement-renovations-how-to-prevent-mold-when-retrofitting-basements/

(6) https://www.kentuckypower.com/save/eNewsletter/ViewStory.aspx?StoryID=1086

 

Replacing old, leaky windows improves the quality of basement living space and saves energy.  Source: Creative Commons, no attribution required.

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