Keeping a Home Cooler in Summer Without Running the AC
In an older house, the discomfort is usually structural rather than mechanical. The walls and the glazing absorb heat through the day and release it into the rooms in the evening, exactly when the occupants want to sleep. The interventions that work are the ones that interrupt that cycle, and most of them are cheaper than a larger air conditioner.
1. Stop the heat before it crosses the glass
Solar gain through west and east glazing is the largest single contributor in most homes. External shading is far more effective than internal blinds, because a blind inside the glass stops the light but the heat is already in the room. Shutters, a deep eave, an external screen or a deciduous tree on the west elevation all work on the same principle: intercept the radiation outside the envelope.
Where external shading is not possible, a reflective or solar-control film applied to the glass reduces admitted heat at moderate cost. It also reduces daylight, which is the trade-off to consider before applying it to a main living room.
2. Use the glazing you have, properly
Close windows and draw shading on the sun-facing side during the day, then open on both sides of the house at night to create cross ventilation. The stack effect does the work if the openings are on opposite elevations and at different heights. This costs nothing and is routinely ignored in houses with air conditioning, where the instinct is to keep everything closed.
3. Deal with the hot air that accumulates
Warm air collects at the top of stairwells and under the roof. A thermostatically controlled roof-space vent or a whole-house fan that exhausts from the highest point is a modest cost and reduces the load on the air conditioner substantially, because it removes heat before the refrigeration cycle has to.
4. Reduce internal gain
Incandescent and halogen lighting converts most of its energy to heat. Cooking without extraction adds moisture and heat. A dishwasher or dryer run at midday adds both. Shifting those loads to the evening, and extracting cooking moisture at the source, makes a measurable difference in a small house.
5. Fix the air leaks the air conditioner is fighting
Air leaks at window perimeters, door sills and ceiling penetrations admit hot humid air continuously. Sealing them is inexpensive and improves both cooling and heating performance. Check the sealant line at every window and door frame, the gaskets on operable units, and the draft at the bottom of exterior doors.
6. When glazing replacement is the answer
If the existing units are single glazed, or the frames are uninsulated aluminum, replacing them addresses the problem at the source: a lower solar heat gain coefficient reduces admitted heat, and a thermally broken frame stops the frame itself acting as a radiator. This is the most expensive option on the list and the only one that also improves winter comfort and acoustic performance, so it belongs in a longer-term plan rather than a quick fix.
If you are deciding between shading, film and new glazing for a specific house, send the orientation of the main rooms and the existing window specification. We will tell you which of the three gives the largest reduction for the money in that situation.
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