York Community Energy

What makes a well-insulated home?

house wrapped-up

Only around 36% of York homes are classed as well-insulated, according to research by Friends of the Earth. This means that most of us in York (and across the UK) live in houses that are expensive to heat, generate unnecessary carbon emissions and are potentially bad for our health. On this page we will briefly look at what makes a house good to live in, what we need to think about when carrying out improvements, and what sort of budget is required.

What makes a good home?

Passivhaus Plus in Fulford - it actually generates more energy than its inhabitants need (photo by L. Outing)

Passivhaus Plus in Fulford – it actually generates more energy than its inhabitants need (photo by L. Outing)

A good, energy efficient home should keep us dry and warm in winter but cool in summer, without needing to use lots of energy to achieve this. Increasingly, it should also be resilient to the impacts of extreme weather events driven by climate change such as flooding or high winds. Most importantly, it should help keep us healthy by providing good indoor air quality alongside thermal comfort. It is much easier to build homes like this from scratch using a high standard such as Passivhaus. A happy owner of one in Harrogate describes his home as “oozing wellbeing”. Sadly, most new homes are not built to that kind of high standard but that’s a topic for another blog.

Most of us live in houses that have stood for decades if not centuries, and will still be standing in 2050 when the UK is supposed to be carbon neutral. We have some of the oldest and coldest housing stock in Europe, which needs a massive overhaul to become good homes for both their residents and the planet. It would be great if the answer was just to stick some insulation and solar panels everywhere, but house retrofitting is rather more complicated than that. Each building is effectively a unique system. Changing one part of it has consequences elsewhere, which means a holistic, ‘whole house’ approach is needed to make sure that we don’t actually make things worse. Let’s look at the main ingredients of a good house retrofit.

(Super) insulation and its continuity

If you think of insulation as a winter coat for your home, then you choose the one suitable for the given climatic and local conditions. For example, in a relatively dry (for the UK) area like York you will be able to consider a wider range of insulation and wall finishes than in rain-swept Scotland. There are different materials and designs to pick from but to do the best job you want all of the house elements in contact with the outside world – from floors to the roof and walls – to be wrapped up, if possible.


Housewarming party participants

Housewarming party participants

Heat and moisture are always on the move and find the path of least resistance out of or into your home. If you insulate just one part of the house, they will travel more freely through the rest. It’s not always practical or even possible to insulate everything, or to do it all in one go. However, it is always best to plan for it to make sure that the works you do in the short term don’t cause more problems than they solve and don’t make future works harder or impossible. For example, before insulating a suspended timber floor during a “Housewarming Party”, a radiator was moved away from underneath the window to be ready to insulate that wall in the future.

Even more importantly, continuity of insulation is key to its satisfactory performance. There would be little point in investing in a thick layer of insulation if you then leave gaps in between, or have a draughty thin door in the middle of it. Just like a hole in your coat, even quite small defects and disjoints in insulation, so called thermal bridges, can leak your precious heat out. They could also bring moisture into the structure of the house where it can cause damage.

Good, skilled installation is essential to avoid problems arising later. Unfortunately, there are many documented cases of bad installation jobs done through a previous government-backed scheme, which have led to problems with mould and condensation, amongst other things. There are calls for the 2020 Green Home Grants scheme to offer guarantees against that through accreditation and good consumer protection. We certainly need more skilled contractors who will do the job carefully and thoroughly. In the meantime, householders can best protect themselves from shoddy work by learning about good retrofitting techniques. One small silver lining of the pandemic has been the rich offer of webinars on the topic, from good guides for beginners by Carbon Co-op to the more advanced series from AECB.

When it comes to deciding on the right insulation amounts, go beyond building regulation standards whenever possible because they are not ambitious enough. In order to tackle climate change in our homes and reap the benefits of doing so, we need to do the best we can, not just meet minimum requirements. Depending on the works recommended for your house, there is likely to be a relatively small difference between the cost of materials for a standard installation and super insulation levels. Most of the cost (or hassle) will be in the actual installation work so you may as well go for the best possible insulation value.


A thermal camera image of heat loss around a loft hatch – orange/yellow areas are warm while blue/purple indicates cold spots, in this case showing draughts around the edges

A thermal camera image of heat loss around a loft hatch – orange/yellow areas are warm while blue/purple indicates cold spots, in this case showing draughts around the edges

Being airtight may not sound like a desirable quality for a good home but it’s actually incredibly important. It basically means removing any air flows caused by gaps and cracks in the so called building fabric; that is your walls, roof, floors and other structural parts. Warm air and thus heat escapes through them which both reduces comfort and increases energy bills. Obviously, you still need to ensure a good air supply but that is best done with controllable ventilation (more on that later) rather than uncontrollable draughts.

Without getting too technical, imagine that you can combine all the draughts, from cracks in plaster to actual holes around poorly fitted windows or in open chimneys, into one. According to the Building Sustainability Podcast, a house conforming to current building standards would effectively have a hole in the wall the size of an ATM machine. This is one way to ensure constant fresh air supply but your heating system then has to be able to compensate for that amount of heat loss. This is expensive, both in monetary and carbon terms– around a third of all UK’s carbon emissions are a result of heat related activities and around a half of those are domestic.

It may also be totally unaffordable for people in fuel poverty who live in very cold homes. A lot of houses do not even conform to those fairly low building standards and may leak twice as much or more. At the other extreme, the equivalent consolidated leak in a highly efficient Passivhaus standard would be the size of a credit card. Most Passivhaus houses therefore have very low energy requirements to keep their occupants warm thanks to their high levels of insulation and airtightness.

You may not be able to aim that high with your retrofit but almost anyone can improve the airtightness of their home with draught-proofing measures. They will not plug those massive holes, so to speak, but they’re a good way to make a start and get comfier. York Community Energy will be offering draught-proofing workshops in the autumn and we can lend you a thermal imaging camera to help you actually see where your home is losing heat.

Interestingly, cold surfaces affect our sense of comfort more than the temperature of the air around us. This is why sitting next to a single or even double-glazed window in a heated room will still give you a chill, and why carpets help keep toes warmer on uninsulated floors. Draught-proofing alone is not enough to actually keep us warm and save energy.

Ventilation and moisture control

Used MVHR filters from a York Passivhaus – an illustration of York’s air pollution levels. The one on the left filters outside air coming in and the other inside air going out.

Used MVHR filters from a York Passivhaus – an illustration of York’s air pollution levels. The one on the left filters outside air coming in and the other inside air going out.

While you’re busy removing draughts and wrapping up your house, you do need to think about keeping a healthy indoor air quality with ventilation. There’s been a lot of talk about air pollution in cities recently but not as much about the fact that most of us spend up to 90% of our time indoors, or even more during the current pandemic. For our wellbeing and health it is crucial to have a good fresh air supply. Apart from the outside sources of air pollution, there are many inside our homes – from cooking smells to various potentially noxious chemicals found in care products, carpets or furniture as well as dust, mould spores and bacteria or viruses. A good supply of fresh air helps remove the risk of developing health conditions stemming from all those.

The tricky bit is balancing the benefits of incoming fresh air with keeping your precious heat. There are various ways to achieve this with different types of ventilation: from the simple opening of windows or trickle vents to humidity-regulated vents and the advanced, mechanical ventilation with heat recovery (MVHR) where incoming air is warmed by outgoing stale air. MVHR systems also filter the air so are particularly well suited for people with respiratory conditions. The higher you aim on airtightness and insulation, the more you need to plan for good, reliable ventilation.

Ventilation also has the all-important role of controlling moisture levels. As the retrofit maxim goes, “insulation without ventilation equals condensation”. Too much moisture creates ideal conditions for moulds and fungi to grow while too little is great for viruses. Happily, maintaining optimum moisture levels for humans eliminates other indoor pollution risks and helps protect the house fabric.

For a nice summary of all the above issues in relation to moisture and healthy homes, watch the great short video below:

How much does all this come to?

As you can see, there is a lot more to a well-retrofitted home than may meet the eye. We haven’t even touched on energy supply, which warrants its own page. Insulation, airtightness and ventilation measures will mostly be hidden behind their finish but, if done well, will pay you back handsomely in increased comfort and potentially improved health. Oh, and of course they should also reduce your energy bills and environmental footprint. People often question the payback time on house retrofits, yet few ask for monetary payback from their new car or refurbished kitchen.

Starting with several hundred pounds per room if you can do it yourself, insulating a whole house well – incorporating good air-tightness and ventilation – will come to tens of thousands of pounds. You may not want to or be able to afford to go the full hog but the government voucher scheme could help you get started on making your house fit for future – remember that your home is not just yours but will belong to many others after you.

In environmental and societal terms, retrofitting the majority of UK homes is more than worthwhile – it’s essential. Currently it is very costly so we need government at all levels to help with the economics. One step would be removing the VAT on eco retrofits, which this petition calls for. This would reduce costs by 20% without any extra funding (demolitions and new builds are often zero-rated which helps explain their popularity over retrofitting).

There is a lot to be done to make retrofitting a popular and viable choice but good house retrofits bring many benefits. They need to form a major part of all plans, both national and local, for reducing carbon emissions which will also improve housing quality and provide skilled jobs. Together we can all contribute to making Britain zero carbon as quickly as possible while improving our homes – it’s a win win.


This post was adapted from a blog post originally written by York Community Energy Treasurer for St Nicks website.

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