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Keep daytime sun and avoidable heat out, then use cooler nighttime air to remove stored heat—only when outdoor conditions are safe and suitable. The approach works best where nights are cool and breezy; close windows again when outdoor air turns warmer, polluted, or too humid.
Why the day-and-night temperature swing can help
During the day, sunlight through windows and heat from cooking, lights, and electronics can warm a home. At night, cooler outdoor air may help carry that heat back out. The U.S. Department of Energy calls this approach fresh-air cooling, or night flushing: outdoor air cools both the home and the heat stored in its materials. It can help keep a home cool through much of the following day, but results depend on the building and weather. As the DOE puts it, “Natural ventilation works best in climates with cool nights and regular breezes.” DOE: Cooling Your Home
Prepare by shading windows that get direct sun
Preventing solar heat from entering is a useful first step. England’s heat checklist recommends shading or covering windows and lists blinds, curtains, external shutters, roller blinds, and awnings as options. Choose what fits your window, sun exposure, ability to open the window, and any renter or installation restrictions. Keep required escape routes and window operation usable. UKHSA: Beat the heat—keep your home cool
What to do during the warm part of the day
- Keep sun-facing windows shaded, using blinds, curtains, shutters, or awnings that suit the window.
- Reduce avoidable indoor heat by limiting unnecessary lighting, electronics, and cooking when practical.
- If outdoor air is hotter than indoor air, opening windows can add heat. Keep them closed if that better preserves the cooler indoor conditions, and use available cooling equipment as appropriate.
How to cool the home with night air
Once outdoor air is cooler than the air indoors, natural ventilation may remove accumulated heat. Openings on different sides or levels can create a through-flow; warm air may also escape through higher openings as cooler air enters lower ones. Fans can help draw in or distribute cool outdoor air. Whether this works depends on your layout, available openings, breezes, and local conditions. DOE: Cooling Your Home
#1 Best Overall
- An Alexa thermostat - Amazon Smart Thermostat is an easy way to switch from a traditional thermostats for homes and help reduce energy usage.
- Create comfort zones throughout your home by connecting to select Alexa devices to automatically adjust heating and cooling based on temperature readings or presence detection.
- Save money and energy - After purchase, Amazon will send you an email with details about home thermostat rebates that may be available from energy providers in your area.
- Save energy - According to EPA estimates, ENERGY STAR certified thermostats save an average of $90 on yearly energy bills.
- Programmable thermostat and automatic control - Create your own home, away and sleep schedules, or have Alexa automatically control the temperature with Alexa+ advanced features.
- Check that outdoor air is cooler than indoors and that local air-quality and weather conditions make opening windows appropriate.
- Open windows on different sides or levels where possible to establish airflow through the home. If openings are on one side only, airflow may be more limited.
- Use a fan to move air through the space if helpful. A portable fan moves room air; a window fan can be used to ventilate through an opening if it fits and can be secured.
- Before outdoor conditions change, close windows and draw shades to reduce incoming heat. This can help retain some benefit from the cooler night air and limit later sun exposure.
Consider practical constraints such as window security, insects, rain, and noise when deciding whether and how long to ventilate.
When not to open windows—or rely on a fan
Do not use natural ventilation to cool the home when outdoor air is polluted or smoky, or when outdoor heat or humidity would make indoor conditions worse. The DOE advises against natural ventilation when outdoor air quality is poor. The U.S. Environmental Protection Agency also recommends evaluating outdoor pollution sources when considering ventilation. Follow local air-quality alerts and any instructions for your home’s ventilation system. DOE: Cooling Your Home EPA: Guide to Air Cleaners in the Home
Rank #2
- CUSTOMIZE: Choose to receive change air filter reminders and select display settings to optimize this thermostat for home.The RTH20B is a direct replacement for the RTH2300, and replacement for the RTH221 offering 5-2 scheduling
- SCHEDULE: Personalize programming in 5-2 day increments - there's even a non-programmable option
- EXPERIENCE: A large screen and clear font enhance daily use
- INSTALLATION: The Honeywell Home UWP wall plate provides an easy install process and simplifies future device upgrades
- FEATURES: 5-2 day scheduling, backlit display, custom display settings, change filter reminder, extended 32°F low-heat setpoint, 1-year warranty
Fan guidance can vary by location and conditions. England’s UK Health Security Agency checklist advises using electric fans if the air temperature is below 35°C and says not to aim a fan directly at the body because this can lead to dehydration. This is England-specific public-health advice, not a universal international threshold. Follow local heat-health guidance. UKHSA: Beat the heat—keep your home cool
Fans move air; they do not make hot, humid outdoor air suitable for cooling. The DOE says ventilation is not an effective cooling strategy in hot, humid climates, although other approaches can reduce the need for air conditioning. DOE: Air Conditioning
Rank #3
- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Connectivity : Wi-Fi - 802.11b/g/n 2.4 GHz, 802.11a/n 5 GHz Wi-Fi., Wireless interconnect : Bluetooth Low Energy Please refer to the product description section below for all applicable legal disclaimers.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home. Lock feature: No
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
Keep ventilation working while improving efficiency
Sealing leaks may improve thermal performance, but do not block vents or make a home’s ventilation worse as an energy-efficiency measure. Ventilation helps remove indoor moisture and pollutants; insufficient ventilation can contribute to condensation and mould. England’s ventilation guidance advises leaving trickle vents open and unblocked and following the manufacturer’s instructions for mechanical ventilation. Australia’s YourHome likewise recommends pairing airtightness with reliable ventilation. UK government: Ventilation, Approved Document F YourHome: Insulation
Which homes may need extra attention?
England’s heat checklist identifies top-floor flats, homes with windows on only one side, homes with little shade, and homes with large unshaded east-, west-, or south-facing windows as potential overheating risks. It also notes that some highly insulated homes can trap heat. These are risk factors, not a diagnosis for every home. Older adults, young children, people with long-term health conditions, pregnant people, people taking certain medications, and people who cannot readily adapt their behavior may be more vulnerable to heat. UKHSA: Beat the heat—keep your home cool
Rank #4
- 【Notice】Please make sure to read the installation and wiring instructions provided in the pictures carefully before buying. If you are inexperienced with installation, it is advised to be cautious when making a purchase to avoid issues like product failure or incompatibility. (Verify the existing base to ensure only 2 to 5 wires are compatible for installation and wiring).
- 【Thermostat Applications】for with Conventional Single-Stage Heating (Gas/Oil/Electric Furnace) & Ventilation & Air Conditioning, up to 1 Heat and 1 Cool. ( TIP: Does not work Multistage Heating & Air Conditioning, and HVAC Central Air Conditioner Heat Pump System )
- 【Incompatible Systems】Does not work multistage systems (1H/2C, 2H/2C), HVAC heat pump systems (2H/1C, 4H/2C), PTACs, 3-wire hydronic (hot water), dual fuel/hybrid heating. Does not work line voltage systems (120-240V electric baseboards heat); mini split heat pump air conditioner, RV air conditioners mach and roughneck series.
- Suuwer S701 Single Stage Non-Programmable Digital Thermostats for Home 1 Heating and 1 Cooling Single-Stage Systems. ( Dual powered by 24VAC power or 2 AAA batteries, No common wire (c-wire) required on most systems).
- Easy-to See and Read: Display with blue backlight, large clear backlit digital display, very suitable for middle-aged and elderly people.
If someone becomes unwell in the heat, treat that as a health concern rather than a home-comfort problem and follow local medical guidance. The England checklist links to NHS advice on heat illness. NHS: Heat exhaustion and heatstroke
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When to investigate a persistent comfort problem
If the home stays uncomfortable despite shading and suitable night ventilation, look for the specific constraint: direct sun, limited openings, one-sided windows, a top-floor location, or heat-producing equipment. For air sealing or window replacement, preserve required ventilation and follow system and product instructions. A qualified energy or ventilation professional can assess the building and recommend changes that account for moisture and indoor air quality.
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Best Value
- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page.Connectivity Protocol : Wi-Fi.Connectivity Protocol : Wi-Fi
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory. Lock feature: No
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home; easily program an energy efficient schedule in the Google home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
- Savings Finder looks for more ways your thermostat can help you save, and suggests tweaks to your schedule in the app; check with your energy provider to learn more about rebates and more ways to save on a Nest thermostat
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
