Q. Hi Kieran
In this beautiful warm weather we are having at the moment, how do you keep an A2 rated house comfortable to live in?
A friend of ours had an indoor temperature of 30 degrees recently, so it was cooler outside.
Is there a system we can build into the house like the heat recovery system?
Alice
Tralee
A. Hi Alice
Thanks for this great question. It is indeed a frustration that some homeowners have invested in an A rated home only to find it too warm in summer. So, what has gone wrong here? After having followed all the advice and investing large sums of money, have we over-insulated our homes?
When I think of insulation, I think of it as a heat barrier. It keeps heat in your home in winter but similarly it should keep heat out in summer. It’s a bit like a Thermos Flask, you can use it to keep coffee hot in winter or beer cool in summer. When you insulate your home you effectively seal your house from temperature fluctuation through insulation and airtightness. In winter you fill your house with imported heat through your heating system. The heating system will send heat into your home until your thermostat tells your heating system that the house is warm enough and it shuts off the supply of heat. So, if this works perfectly well in winter, how does it all go wrong in summer?
In summer you have a very different situation. Now it is getting warmer outside so you want the insulation to keep the excess heat outside to keep the inside of your home at a comfortable temperature. What I believe is happening in your friend’s home is that it is benefiting from too much solar gain from south facing glazing in their living space. We are now the victims of new building technology.
New homes now are generally orientated so that the living spaces benefit from the most sun and we all know that the must-have is large patio doors and picture windows to capture as much views and light as possible. This is wonderful in winter when daylight is so precious and even helps our heating systems because all this south facing glazing allows some heat to pass though in the form of solar gain but in the summer this is problematic. It is like leaving your heating system on with no thermostat in place so it just keeps filling your home with heat and because you have so much insulation in place, your house just gets hotter and hotter. So, what’s the solution?
The fix is in fact relatively simple and rudimentary. Heat recovery ventilation is not really going to help as all it will do is to move the heat in your house from one room to another so it will likely dilute it a little in the living space but send it to all the other habitable rooms too. I have heard some people considering air conditioning but again I feel this is a heavy handed approach in this country and, though it may very well deal with the issue, it is going to cost a lot to install and run in a house where you have already invested heavily into energy efficiency. I’d be looking to the source of the problem for the solution.
The vast majority of the heat is coming through the south facing windows in the middle of summer. If you opt for triple glazing this will certainly help with solar gain (or heat from the sun passing though your windows – like when a car gets too warm inside if it’s parked at the beach in the middle of summer). The next and probably the most important step is to fit a canopy or overhang above your south facing windows and doors. In the continent this is called a ‘brise soleil’ or sun breaker. This will shield your glazing from the worst effects of the sun’s heat in summer, when it’s warmest and highest in the sky. It does take a little light from these rooms but really it is very little if designed correctly and it makes a huge difference to overheating. This overhang can be constricted by your builder or there are a variety of lightweight products available online. The finished design might be louvred to allow a little light in or indeed solid. Either way It’s a game changer.
Now you can have your cake and eat it. You can have all the insulation in the external envelope of your home to maintain ambient temperature in summer and winter. You can have all the south facing glazing you want and enjoy the light and views in your living spaces. Your bris soleil will keep the extremes of mid summer heat at bay and you can probably even give your heat recovery ventilation a hard earned rest as you open most of the windows with the warm air outside. It won’t be long before the tide will turn and you’ll be glad of the insulation as the frost reappears on the morning grass.
Kieran McCarthy is a building engineer and director of KMC Homes luxury A-Rated new home builder, serving Cork and Limerick. He is also presenter of a new RTE tv show showcasing deep retrofits in Irish homes due out later this year.
Check out KMC Homes’ brand new website kmchomes.ie
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