It’s been an interesting summer, in more ways than one, seesawing between some of the hottest days on record and below average temperatures. MetOffice happened (or chose?) to issue its 2019 State of the Climate report on the hottest day of July. This confirmed the overall warming trend and the role of climate change in making extreme weather events such as heatwaves much more likely to happen and more often. The MetOffice projections show that these “could occur on average as regularly as every other year by the middle of the century.” What does this mean for our homes?
Comfortable temperatures are hard to define because they vary hugely depending on our individual levels of activity or digestion, general health and many other personal as well as environmental factors. What feels nice to one person will seem too hot or cold to another, and the air temperature forms only one part of what experts call thermal comfort. When it comes to what’s too hot, generally speaking according to Kate de Selincourt’s detailed article on overheating in buildings, “most people begin to feel ‘warm’ at 25ºC and ‘hot’ at 28ºC”. Going much beyond those temperatures poses the risk of heat stress and potentially dangerous health impacts or even excess deaths, especially if we can’t sleep at night due to the heat.
Now, it may seem counter-intuitive to suggest that the solution is to effectively put a duvet over your house by insulating it. However, when installed well and with a whole house plan in mind, insulation will not just keep you warmer in the winter but also cooler in the summer. Just like using a hat will help protect us from a sunstroke, insulated roofs and walls will help keep the heat out of the house. The trick is to balance all the main factors that help make a good house – continuous insulation, airtightness and ventilation discussed in our previous blog – to give the best year round performance.
York architect Phil Bixby, a regular participant of our York Open Eco Homes, has shown how effective his energy efficient retrofit of a Victorian end terrace has been in keeping his household cooler on a hot summer day. Despite the outside temperature reaching over 35ºC, the living room kept around 10ºC cooler throughout the day. One could argue that uninsulated Victorian terraced houses can often remain cooler in the summer; but they will also be pretty cold in the winter unless you can afford to pour heat into it them at a significant cost for both your pocket and the planet. Keeping reasonably comfortable in our homes throughout the year is surely more desirable than keeping cooler during particular extreme weather events.
There is much more to the issue of overheating than too little (or, in rarer cases, too much) insulation. Kate de Selincourt cites examples from around the country of the different causes of building overheating – from too much solar gain or lack of adequate ventilation to uninsulated hot water pipes and even urban heat island effect (which green spaces such as St Nicks can help reduce). I recommend her article for anyone who is keen to delve deeper into the technical issues associated with good house retrofitting before applying for a Green Homes Grant to upgrade their home.
The upshot of it is that making our homes warmer with insulation can also help keep them cooler when required — if it is done carefully, both at the design and installation or construction stages. As with many things, the devil is in the detail. The Green Homes Grants, available from the end of September 2020 until March 2021, will not cover full costs of insulating your whole home but should easily pay at least for getting the attic and ground floors done. Keeping feet warm and stopping heat escaping through the roof are very good and low risk starting points on a whole house retrofit journey.
To get more tips and see what Phil and other York residents have done to make their homes more comfortable, cheaper to run and more climate-friendly, join us online for York Open Eco Homes 2020.
This post was written by St Nicks Outreach Officer Ivana Jakubkova.