The UK has experienced some scorching weather this summer, with the Met Office predicting that ‘warmer than average’ temperatures will continue into the autumn. While this unusually hot and sunny weather has been enjoyed in the day, many of us have struggled to sleep in uncomfortably warm bedrooms at night.
At Knauf Insulation, we manufacture solutions that contribute to the thermal efficiency, fire safety, acoustic performance, and comfort of buildings. Amongst the UK public, there is an understanding of the benefits quality insulation can offer in cooler months. Less understood is the role of insulation in making a home more comfortable in the kind of hot climate we have been experiencing this year.
In summer months, all buildings heat up through ‘external gains’ and ‘internal gains’. External gains are primarily a result of the radiant energy in sunlight being absorbed by the building. This can be either on internal surfaces when shining through glazing, which will be dominant in most domestic environments or directly on the external surfaces. Internal gains are heat generated by lighting, and electrical or gas appliances in the home, or its occupants.
Minimising these gains is a good starting point for keeping cool in the summer. External gains can be limited through effective shading, where blinds or curtains are drawn as the sun moves around the house. Insulation of hot water pipes and boiler connections to hot water cyclinders will help manage internal gains.
But, to cool a hot house, the best thing to do is purge heat through ventilation. Although easier said than done – particularly in an urban setting – doors, windows and rooflights should be opened to encourage a cross-breeze that replaces the air in the building. This is best done at night, when the air outside is more likely to be cooler than the air inside the house.
As manufacturers of insulation solutions, and with a strong commitment to making buildings more comfortable for its occupants, what’s our perspective on how insulation can benefit homes in hot weather? Although perhaps counterintuitive right now, our advice is to look to the loft…
Insulation is very good at controlling the transfer of heat. So, a well-insulated house means a warm building stays warm in the winter, and takes longer to heat up from the effects of the sun on its walls and roof in the summer. Conversely, it also means it can take longer to cool down in the summer. But we believe the heat controlling characteristics of insulation have a particularly important role to play in managing the transfer of heat from lofts into the bedrooms below.
Lofts get very hot in the summer, with temperatures often exceeding 40 degrees Celsius. As the sun shines directly onto the roof’s dark surfaces throughout the long days, heat is absorbed and radiated into the roof space. Without adequate insulation, this temperature accumulated in the daytime can quickly transfer into any bedrooms on the upper floor.
It is also common for loft insulation to be disturbed by tradesmen. Plumbers or electricians, for example, may displace the installed insulation material, resulting in places where there’s no insulation and places where there’s too much insulation. This creates localised hot spots, where heat passes freely and rapidly from the loft space, through the ceiling and into the room below. Maintaining loft insulation is therefore important all year round.
We recommend conducting an annual check. First, by measuring the existing loft insulation. It should be at least 250 - 270mm thick. Next, by checking that the insulation is laid evenly across the loft space and by redistributing it if necessary. If any areas still need a top up, our glass mineral wool insulation is widely available from local DIY stores, builders merchants, or can be supplied by a loft insulation installer.
Just as ventilation is needed in the inhabited rooms of a house, consideration should also be given to the flow of air to the loft space from the outside via the eaves. As well as preserving the properties of the insulation material by allowing the building’s natural moisture to escape, having ventilation in the roof’s eaves will also help to lower temperatures inside the loft.
By all accounts, the ‘unusually’ hot weather we have been seeing this summer will become less unusual in the years ahead. While not the complete solution to an overheated home, adequate and properly installed insulation plays an important supporting role to ventilation in our fight against hot, uncomfortable bedrooms.