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Summer Ventilation and Cooling

Using Air to Air ERV to precool the Fresh air in Summer time. Image Wikimedia Commons/MoeSalem

Michael Canavan

Now that summer is approaching, homeowners need to consider the summertime ventilation and cooling needs for their homes considering energy usage.

Natural ventilation is as simple as opening windows on your house in a way that creates a cooling natural draft throughout the house. If you open the upper level windows in your house on the sunny side and the lower windows on the shaded side of the house, with interior doors open, you will create a natural draft throughout the house. Warm air rises and cool air sinks which creates the draft. The strength of the draft will depend on the house layout. If you open the furthest windows on each level it will help create the largest air movement. This method has been in use for hundreds of years before air conditioning became common in homes in the 1960s. Adding a whole-house fan will give you a higher airflow in the house. This method is good when the air is less humid, say, below a dew point of 60 degrees. Fresh air is one of the ways thought to reduce the Covid-19 transmission by replacing stale air with fresh.

As the humidity rises, you will want to dry the air out. This is where the air conditioner unit comes in handy, as it cools the air by transferring heat energy to the exterior and also lowering the humidity. General recommendations are to use air conditioning when the outside temperature is above 78 degrees Fahrenheit and the relative humidity is above 60% but adjust the settings for what makes you comfortable for most of the time. A central air conditioning system has an exterior (condenser) unit that should be shaded, with open space around it, to allow the heat to dissipate away from the condenser unit. The unit should be monitored for clean coil fins weekly, looking for grass cuttings, large pollen seeds (milkweed) and general dirt. Hose off the unit as needed with the unit turned off. On the interior, the air filter in the furnace will need to be changed or cleaned, and make sure the supply and return duct vents are not blocked. For window type units, clean the filter at least on a monthly basis, adjusting based on the level of material on the filter. Clean filters keep both types of systems running more efficiently with better air heat exchange. If you have an air conditioning unit that is more than 10 years old, you should consider replacing it due to the improvements in technology that make the new units much more energy efficient. Always look for the Energy Star rated units.

“Split” heat pump units are becoming more common these days due to greater efficiencies of the units. Heat pumps are for both heating and cooling; they are similar to conventional air conditioners with a valve that lets the coolant flow in the opposite direction depending on whether the thermostat is calling for heating or cooling.

Air conditioning systems should be sized for the building heat and cooling loads. Window units and central air systems are generally sized for one ton (12,000 BTU’s) of cooling load for 600 square feet of living space. Heat pumps are sized similarly but consider some building conditions, for instance, window glazing, which helps to increase the efficiency. Air conditioners should be set so they dehumidify the air and cool it to about 10 degrees below the outside air temperature, which provides most people with relief from the heat. Dry air will feel cooler even if the temperature is higher, not necessarily 68-74 degrees Fahrenheit on the set-it-and-forget-it thermostat.

There are some other things to consider for staying cooler in the summer. Deciduous shade trees provide cooler air underneath them. compared to being out in the sun. Foundation plantings are great to shade the concrete foundation walls, which will also keep your house cooler. The screens on your window will provide some shading to the glass, the least insulated part of a wall. Closing your blinds or curtains will also block heat from circulating into the home. Hard surfaces like asphalt and concrete driveways and walks hold and reflect heat into and around your house.

Michael Canavan is the owner of Eagle Home Inspection Solutions of Norwich Vermont. Learn more at or (802)526-2642.

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