Topping out

Gerald Cole

Cold comfort

Six hot tips to keep your new home cool

Some 30 years ago, shortly after my wife and I bought our current house, my in-laws offered us a moving-in present: a set of shutters for the main facade. Naturally I was appalled.

They were entirely decorative, just two bracketing each window – which each boasted four panes – and intended to be fixed permanently in position. To my youthfully prejudiced mind they were not only useless but, worse, unbelievably twee. Nowadays, of course, if anyone made a similar offer, I’d bite their hand off.

What a difference a heatwave makes. With summer temperatures now predicted to hit 40ºC on a regular basis, cooling our homes is destined to become as important as heating them – a big ask for a housing stock designed for more temperate times. Luckily selfbuilders are presented with a clean slate. Here, then, are six suggestions to make your dream home fit for a warmer future.

1. Don’t neglect insulation and airtightness

Recent upgrades to the Building Regulations have required increased insulation and airtightness to reduce heat loss and save energy. But this has resulted in summer overheating in some new homes with large amounts of glazing. As a result, this June a new regulation – Part O – was introduced. It limits excess solar gain by restricting the amount of glazing in a single room: a potential death knell for all-glass conservatories and glass-box extensions. But insulation works in two ways. It both retains internal heat and keeps external heat out. Don’t forget, though, that houses also produce warmth internally, from cooking, hot water, refrigeration, electrical items and body heat, all of which requires…

2. Good ventilation

The most effective form of ventilation, if not the cheapest, is a whole-house mechanical ventilation system, where a central fan draws warm air from the kitchen and bathrooms through a network of ducting and vents it to the outside. At the same time, fresh air is drawn into the house and distributed via another series of ducts to living rooms and bedrooms. The result is constantly refreshed air and a constant temperature throughout the building. The system is an updated version of cross ventilation where two or more openings in a room allow air to move freely from areas of high pressure to low pressure, hopefully taking heat with it. But any form of ventilation will benefit from reducing the amount of incoming heat, so it’s wise to…

3. Shutter up

External window shutters deflect the heat of the sun while allowing cooling breezes to enter through the open louvres and warm air to escape. In the UK, however, shutters and blinds have conventionally been fitted on the inside. But this leaves the window glass exposed to the sun. Double and triple glazing and solar control coating will dramatically cut heat transmission, but a significant amount will still reach the inside. Which raises another problem. External shutters require windows to open inwards, but most UK windows are outward-opening casements. One answer is to fit sash windows; another, the more versatile tilt-and-turn. The shutters themselves are usually wooden – preferably hardwood – and so need to be painted or stained regularly, or uPVC which is largely maintenance free but can become brittle over time. Alternatively, insulated metal roller blinds operated either by hand or motorised can add good security to the shading. If the motor is incorporated into a home automation system, the shutters can be closed remotely or automatically as the outside temperature rises. But for large areas of glazing, a simpler, more visually pleasing solution is…

4. Shading

This can come in a variety of forms from open-topped pergolas erected over patios to brise soleil – racks of horizontal slats above windows, angled to block the sun’s rays at their hottest point in the sky. Retractable awnings serve a similar function. Extra-wide south-facing eaves are a more permanent solution, as are trees planted to shade southfacing facades and patios, though do site them from 15 to 20 feet away to avoid problems with roots. But, even with all the measures mentioned above, there comes a point when the only remedy is…

5. Active cooling

Less than five per cent of British homes currently have air conditioning, largely because it’s expensive to install and run and until recently only needed for a few weeks in the summer.

This summer’s temperatures might change a few well-funded minds, but for most budgets portable, single-room units will do. More efficient but more expensive are split-unit air conditioners, which are permanently mounted on outside walls. One option worth considering is an air-to-air heat pump. Though chiefly intended to extract heat from the atmosphere which is then blown around the house, it can also be reversed to provide a cooling breeze. Installation is easy because it only requires an outside wall. But its use is usually confined to single rooms, small flats or granny annexes. It’s also unable to provide hot water, so a separate water heating system will be needed. Unless, of course, you fit…

6. Photovoltaics and solar thermal panels

If your design includes a south-facing roof, fitting PV panels can provide free electricity on sunny days to power active cooling – and any other electrical device, including immersion heaters. A solar thermal panel contains liquid heated by sunlight and used to heat hot water cylinders via an extra coil. According to the Energy Savings Trust, it should produce around 90 per cent of your hot water in summer and 25 per cent in winter. Both systems can make use of the larger cylinders required by heat pump systems.