They Might Block the Cold, but This Common Thermal Blind Mistake Could Make You Sick – And Land You With a Costly Repair Bill

This simple installation trick can prevent headaches down the line

Living room with wooden floor and gothic window with views to the garden. Red and green upholstered chairs and sofa and floral curtains and cushions.
(Image credit: Future / Jonathan Gooch)

During winter, thermal blinds play a huge role in reducing bills and keeping homes warm. However, a simple installation mistake could result in mold and mildew.

Fitting them too close to your windows can quickly trap moisture and condensation, offering nowhere to escape.

Thermal Blind Installation Mistake

Window blind ideas are one of the simplest, stylish ways to draft-proof a home and prevent cold air transfer. But thermal blinds (available from Walmart) have to be installed correctly to feel the effects without mold.

Hanging the blinds too close to the window might make sense when trying to weatherproof your windows; however, John Parks from Advanced Insulation System points out that this curtain mistake reduces airflow, which can create mold.

He explains, 'The warm air inside the home hits the cold glass, moisture gets trapped, and condensation starts to form. Over time, that moisture will build up and you’ll start to see mold forming around the sill or window frame.'

Luckily, it is easy to stop condensation and prevent mold, John assures. All you have to do is leave around one inch of space between the blind and the glass.

'You also want to make sure the window area is sealed and insulated properly,' he continues. 'Cold air leaking in around the frame makes condensation worse. If you live in a humid area or notice fogging, putting a small dehumidifier nearby can help keep things dry.'

You don't need harsh chemicals to remove mold, either. The best cleaning tip to tackle mold on walls, window frames, or blinds is to try using 30% white vinegar from Walmart. Spray the area with pure vinegar using a spray bottle, also from Walmart, and allow it to sit for at least half an hour before scrubbing away.

Cleaning with white vinegar is far more effective than bleach due to its anti-fungal properties. Plus, it is less damaging to your home, decor, and health.

A white attic space with a teal statement wall and radiator, a white and blue striped blind and a stacked suitcase set. To the right is the corner of a blue bedframe with grey bedding.

Installing thermal blinds correctly can instantly make any room feel warmer.

(Image credit: ONE REPRESENTS LTD / Future)

Besides correct blind placement, John adds that sealing window gaps to stop cold air leaks should also be at the top of your fall home maintenance checklist. This will bolster your thermal blinds' efforts to cut energy bills and make heating more efficient.

He urges, 'It’s also a good idea to check the caulking and weatherstripping [from Walmart] around your windows. Over time, those materials crack or pull away, and that’s how drafts sneak in. Re-caulking and replacing old weatherstripping make a big difference.' The 3M Marine Adhesive Polyurethane Sealant from The Home Depot, is ideal for this.

'You can also apply a layer of clear insulation film [from Amazon] over the glass in the colder months. That helps regulate the window temperature and stops moisture before it builds up. Keeping the area clean and dry will go a long way in preventing mold.'

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Meet the Expert

John Parks
John Parks

John is the COO and co-owner of Advanced Insulation System in San Diego, which is a residential and commercial insulation company that also specializes in mold remediation, attic and crawlspace cleaning, and moisture control. He has over 10 years of experience working within this industry, so can speak to the many common complaints of homeowners with musty odors in their homes.


Improving ventilation is a great trick for preventing mold all over your home, year-round. When you are focused on keeping warm in winter, consider using shock ventilation to help boost air quality without impacting your heating all day.

Chiana Dickson
Content Editor

Chiana has been at Homes & Gardens for two years and is our resident 'queen' of non-toxic living. She spends most of her time producing content for the Solved section of the website, helping readers get the most out of their homes through clever decluttering, cleaning, and tidying tips. She was named one of Fixr's top home improvement journalists in 2024.

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