HVAC pros reveal the exact temperature your thermostat should be to stop damp, mold, and condensation this winter – and 5 signs it's time to flip the switch

As fall deepens and the air turns crisp across the country, many of us are preparing for what's shaping up to be a different kind of winter. With climate patterns like La Niña influencing the season, many parts of the US could see a colder and stormier winter than the last, especially in the northern states and the Pacific Northwest.

As surprising as it may sound, keeping your thermostat at a consistent temperature in winter – ideally between 68 and 72° Fahrenheit – is a powerful way to combat the perennial winter threats of dampness, mold, and condensation, all while preventing significant spikes in your energy bills.

We spoke to our energy and heating experts, who agree that a steady temperature will not only keep your home cozy this fall, but also prevent your HVAC system from overworking during the colder months ahead, whatever your heating type.

The science behind the perfect temperature to keep your thermostat this winter

With cooler, potentially stormier weather on the horizon this season, homeowners need to be proactive about their indoor environment. A simple and effective solution to a major winter woe – common mold – is keeping your thermostat at a constant temperature.

Elizabeth Reilly from GreenSavers, eight-time ENERGY STAR Contractor of the Year, advises, 'For most homes, setting the thermostat between 68-72° Fahrenheit (20-22° Celsius) will work well to balance comfort, energy-efficiency, and to keep dampness and mold at bay.'

This will avoid the thermostat mistake of setting it too high or too low.

HVAC expert and owner of AirConditionerLab, Josh Mitchell, explains why keeping the right temperature indoors is essential in the battle against mold and dampness, which thrive on surfaces with moisture. That moisture often occurs when temperatures fluctuate, creating condensation.

'Dampness and mold grow in areas where moisture is present on surfaces such as windows and walls, and this usually happens when temperatures change and cause condensation to form,' Josh says.

This condensation, if left untreated, can lead to mold and damaged window seals. To prevent this, Josh emphasizes the importance of a stable indoor environment.

'Keeping the temperature stable reduces the chance of condensation forming, which helps control moisture,' he adds, which will prevent household mold from taking hold. It's a great way to stop window condensation this winter.

Josh clarifies that allowing your home's temperature to drop too low, whether overnight or during the day, creates cool spots where moisture can condense. Maintaining a steady temperature prevents these cool spots from forming.

'This approach is particularly useful in colder climates, or in homes with older windows and insulation, where surfaces are more prone to cooling down quickly,' he adds.

However, if your home is poorly insulated or has an old heating system, running the heating constantly may not be the best solution. In such cases, the system could overwork and struggle to maintain the desired temperature. It's also essential to ensure your thermostat is placed correctly for accurate readings.

Having it too close to the front door or windows may register a lower temperature reading than further away, tripping the system to turn on when it's not needed. This is a heating mistake and will push your bills up unnecessarily, as well as make your house heat unevenly.

The caveat to the above temperature range is when you're considering the ideal temperature to set your thermostat to when on winter vacation. This should be lowered slightly, to approximately 59-60˚F.

This will ensure your home retains necessary warmth while making it quicker and easier to bring it back up to temperature when you return home.

Why a steady temperature indoors saves energy

In an era where every degree counts for both our wallets and the planet, we're all looking for efficient ways to keep our homes healthy and comfortable. This fall and winter, a simple change to your heating habits can do just that – while also saving you money.

Keeping your home at a consistent temperature is a surprisingly effective way to save energy and reduce the risk of mold and condensation.

HVAC pro, Josh Mitchell, notes that letting your home cool down too much forces your heating system to work harder to restore the temperature, 'especially in well-insulated homes.'

Data from the US Department of Energy (DOE) confirms that maintaining a steady temperature can significantly reduce overall energy use. The DOE suggests that homeowners can save up to 10% on heating and cooling bills annually by simply turning their thermostat back 7-10°F for eight hours a day from its normal setting

Five signs it's time to switch the heating on

Bert Miskell, owner of BPM Heating, Cooling & Plumbing says, 'As a rule of thumb, if you're waking up to foggy windows or if there are cool spots in your home, it's time to turn on the heating.'

Bert notes in Frederick, MD, 'we've been experiencing a somewhat milder transition out of summer and into fall. Overnight temperatures haven't quite averaged the 40-50° F range, though that appears to be changing in the coming week.'

Keep an eye on regional weather reports, and watch out for these five crucial signs that it's time to switch your heating on:

1. The temperature in your home consistently drops below 64° F.
2. You're uncomfortably cold indoors, and blankets, heatpads, and warm clothing aren't cutting it. For instance, your joints are aching from the cold, or you're struggling to sleep because of it.
3. You have condensation forming daily on the windows, walls, and other interior surfaces.
4. You've spotted mold forming along window seals or in the more humid rooms of the house (such as the bathroom or kitchen).
5. You or a member of your household is vulnerable to the cold, for instance, because of illness or if they're elderly or very young (such as a newborn baby).

Benefits of smart thermostats

For even greater control and efficiency, experts recommend upgrading to a smart thermostat. Bill Taylor, an HVAC contractor manager at South Jersey Gas and Elizabethtown Gas, calls it 'one of the best ways to conserve energy' and a key tool in the fight against mold.

'A smart thermostat is a Wi-Fi-enabled device that automatically adjusts heating and cooling temperature settings in your home for optimal performance from a phone, tablet, or smart speaker,' says Bill. This technology provides the flexibility to adjust the temperature based on your lifestyle and schedule, from anywhere at any time.

Many smart thermostats, like those from Nest, available at Amazon, can save users up to a quarter on their bills. When we tested it in-house last winter, a smart thermostat knocked hundreds of dollars off our tester's bills across the bitterest winter months.

While a consistent temperature is a great strategy, Shawn McLaughlin, CEO of Emporia Energy, advises homeowners to be aware of 'time-of-use' pricing in their area. 'This is a common practice where utilities can charge three to four times the standard rate for energy used during certain peak hours,' he says.

By using a smart thermostat to reduce energy use during these high-cost periods, households can lower their electric bills by 30% to 40%. A smart thermostat’s ability to track usage and household habits makes it a powerful tool for optimizing energy use, avoiding expensive peak-hour charges, and slashing your energy bills this winter.

What to shop

All prices were correct at the time of publication.

FAQs

When should you not keep heating at a constant temperature?

While doing so is often beneficial, this method is not advised for homes with poor insulation or an old, inefficient boiler, as the heat won't be retained and the boiler, which already uses large amounts of energy to run, will be overworked.

Instead, to keep a poorly insulated house warm, use window film as an affordable solution to glass insulation, seal drafts, and use heaters strategically around the home. Keep an eye (and ear) out for any signs your boiler needs replacing, and be prepared to call in the professionals if any become apparent, as wait times in peak seasons such as fall and winter can quickly add up as demand increases.

Experiencing any common thermostat problems? Our expert-led guide breaks down how to fix them fast.

Plus, if you've spotted condensation outside your windows, it might be a warning sign that your insulation type is failing if it doesn't clear as the weather outside naturally warms up.