How to draft proof a basement and reduce your energy bills by 25%

Basements are notorious for letting in cold air, leading to higher heating costs. Draft-proofing your basement is a vital step toward creating a comfortable, energy-efficient home.

Our HVAC experts reveal exactly how to draft proof a basement – and the common mistakes to avoid. By sealing gaps and improving insulation, you can transform your basement into a cozy, functional space.

Knowing how to run and clean your HVAC system, as well as how to draft proof your basement, is key to managing your home climate efficiently.

Why you should always draft proof a basement

Drafts in a basement can make the space chilly and increase energy bills by forcing your heating system to work harder. Draft-proofing not only saves money but also keeps a basement warm, preventing cold air from seeping into other parts of your home. It’s an essential step for enhancing comfort, reducing you home's carbon footprint and is a key way to be more sustainable at home.

Josh Mitchell, HVAC technician and founder of Air Conditioner Lab, says, 'Basements are prone to drafts because they often have older windows, gaps around pipes and ducts, and unfinished walls. These drafts can increase heating and cooling costs by up to 25%, making the floors above feel colder.'

Steve Pacholski, brand president of HVAC experts Varsity Zone adds, 'There’s also the issue of moisture that can come along with those drafts, and over time, that can lead to bigger problems like mold or damage to the structure.'

How to draft proof a basement

Effective draft-proofing begins with identifying problem areas, such as cracks in the foundation, gaps around windows, or air leaks around pipes and other utilities.

Pacholski says, 'If you’re tackling this, start by checking your windows and doors. If you feel a draft, you’ll want to seal it up. If you’re unsure where the drafts are coming from, try the candle test. Light a candle and move it slowly around windows, doors, and other suspected areas. If the flame flickers, you’ve found a spot that needs sealing.

'Weatherstripping around windows is a good first step, and using caulk to fill in any cracks can help a lot. For older windows, it might be worth looking into replacements with modern, energy-efficient options, especially if the drafts are severe.

'When it comes to doors, a door sweep at the bottom and some weatherstripping around the frame can block out most of the cold air. Any cracks you find on the walls or floor should be sealed. Smaller gaps can be handled with silicone caulk or expanding foam. Larger ones may need something stronger like a concrete filler.'

This multi-use GE Silicone All Purpose Caulk from Lowe's is great for sealing around basement windows and doors, while this M-D White Vinyl/Foam Door Weatherstrip, also from Lowe's, is flexible and easy to install – you can even cut it with scissors.

Pacholski continues, 'Finally, don’t forget about the ducts and vents – these are often overlooked but can let in cold air if they aren’t sealed properly. Using foil tape or a good sealant can help here.'

It's important to note the vents themselves should not be sealed up as they may leave your basement at increased risk of mold. Learn how often should air ducts be cleaned.

Mitchell adds, 'Spray foam insulation also works well for gaps around pipes and ducts because it expands to fill irregular spaces. Another common source of drafts is the rim joist – the area where the walls meet the floor joists. Seal it with rigid foam insulation and caulk.

'Foam board insulation on walls and insulated subfloor panels can make a big difference for unfinished basements. Adding a dehumidifier is also helpful to reduce moisture and maintain balanced indoor conditions.'

We've shared some of our top dehumidifiers below. First, there are things you need to know before buying a dehumidifier.

Prices correct at time of publication.

What to avoid when draft proofing a basement

From blocking ventilation openings to using low-grade sealants, there are certain errors that our HVAC experts frequently encounter in house basements.

Francisco Fuenmayor, a home improvement expert at LocalProBook, says, 'Avoid using cheap, temporary solutions like plastic wrap over windows. Not only can it look unattractive, but it doesn't provide long-term benefits. Also, don’t overdo the insulation. Too much insulation can create a sealed environment that causes other issues like condensation.'

For more tips, delve into our smart and easy basement insulation ideas.

Pacholski says, 'It’s important not to block vents or exhausts, as basements need proper airflow to avoid moisture buildup. Also, it’s worth investing in decent materials for sealing – cheaper weatherstripping or caulk might seem like a quick fix, but they don’t last and will likely need replacing in the long run.'

Check out our expert guide to whether you should close vents in unused rooms. and ways to avoid mold growing on your air vents. If you do find mold on your air vents, clean them immediately. You can use a 50/50 vinegar solution spray or soak (leave for an hour).

Pacholski adds, 'Finally, remember that sealing won’t do much good if your basement isn’t properly insulated. Insulation plays a big role in keeping the space warm.'

Top products for draft proofing a basement

High-quality products like foam sealants, weatherproofing strips, and caulking compounds are essential for sealing gaps.

Mitchell recommends this Duck MAX Strength Heavy Duty Insulating Film Window Kit from Amazon. He says, 'This heavy-duty insulating film is perfect for sealing basement windows. It blocks drafts and heat loss effectively, helping reduce energy bills by up to 20%. It’s also easy to install and remove without damaging your windows.'

Pacholski loves Frost King Clear Plastic Weatherseal Tape, available from Amazon, which is completely waterproof and can withstand extremes of heat and cold. It has a special adhesive system effective even at -10 degrees Fahrenheit. He says, 'It's affordable, easy to use, and does a great job of sealing gaps around windows and doors.'

Fuenmayor recommends this AGHITG Window Insulation for Winter from Amazon. He says, 'Specifically designed for basement windows, these insulated window coverings are ideal for reducing drafts and keeping the temperature regulated. The custom fit helps eliminate heat loss while also reducing noise.'

For larger insulation projects, rigid foam boards or spray foam insulation can be highly effective. You can find our pro recommendations below.

FAQs

How can I tell if my basement has drafts?

Check for drafts by feeling for cold air near windows, doors, and foundation cracks.

Mitchell says, 'Look for signs like cold spots, high humidity, or visible gaps around windows and pipes. You can use an infrared thermometer [available at Amazon] to detect temperature differences or a smoke stick to identify air movement.'

A simple candle test – holding a lit candle near suspected gaps – can also reveal air movement.

Do I need special insulation for basements?

Yes, use insulation designed for below-grade applications, like rigid foam boards, to prevent moisture damage. Avoid fiberglass in areas prone to dampness, as it can trap water and encourage mold growth.

Delve into the pros and cons of insulating a basement ceiling in our dedicated guide.

Can I draft proof my basement myself?

Yes, most draft-proofing tasks are an essential DIY skill and with affordable tools, like caulking guns and weatherstripping, it's straightforward to do yourself.

Mitchell says, 'Sealing windows and using spray foam for gaps are DIY-friendly tasks. However, more complex fixes like insulating the rim joist or sub-floor may require professional help.'

How often should I check my basement for drafts?

It’s a good idea to inspect your basement for drafts annually, especially before winter. Regular maintenance ensures gaps don’t worsen over time and keeps your home energy-efficient.

Check out our top tips for how to ventilate a basement.

Will draft proofing reduce moisture issues?

Draft proofing can help by sealing gaps that let in humid air, but it’s not a complete solution. Address underlying moisture problems, such as poor drainage or fix basement leaks, before sealing the basement.

Mitchell adds, 'Sealing drafts does help block humid air from entering the space, reducing condensation and the risk of mold. Pair this with a dehumidifier for better results.'

So there you have it, how to draft proof a basement like the pros. Draft proofing a basement improves energy efficiency, enhances comfort, and prevents drafts from affecting the rest of your home. With proper tools and techniques, you can create a warm, draft-free space without increasing the risk of mold.

Next, learn about the things people with nice-smelling basements always do.