Your house leaks heat. Through the walls, roof, windows, and all the cracks you didn’t realise were there until you started looking. With heating costs accounting for around 55 percent of the average energy bill (Ofgem), most of us are unnecessarily heating the great outdoors instead of our sitting rooms. There’s obviously the financial incentive to properly insulate your house. With energy prices continuing to rise, saving money is a pretty big incentive.
Households in the UK have some of the least efficient homes in Western Europe (Climate Change Committee). That’s a very polite way of saying we’re awful at retaining heat in our buildings. More than 19 million homes in the UK need energy efficiency improvements (National Infrastructure Commission). Poorly insulated homes lead to thousands of excess winter deaths each year (ONS). If the NHS recommends you keep your home heated to at least 18°C(NHS) and average winter temperatures only get as high as 2°C to 7°C(Met Office), then everything about your house is fighting you if it’s not properly insulated.
But insulating your home properly can reduce demand for heating by up to 40 percent (Energy Saving Trust). The bad news is that doing it right means understanding where your home loses heat, what insulation methods are effective in UK climate conditions, and how to prioritise if you can’t do everything at once.
## How Heat Loss Actually Works
Let’s take a look at how heat actually escapes your house so quickly, and why you lose heat fastest through some surprising places.
Heat transfer always goes from warmer to cooler areas. Inside your home, heat moves from inside your home to the outdoors. This happens in three distinct ways, and all of them matter when it comes to insulating your home.
Conduction occurs when heat transfers through solid materials. Your walls, windows, floors, and roof all conduct heat out of your home. Different materials conduct heat at different rates. A solid brick wall will conduct heat far quicker than a properly installed cavity wall. That’s why older houses, like Victorian terrace houses, are much harder to keep warm.
Convection is the process of warm air moving heat with it. When your house loses heat through draughts, that’s an example of convection. Cold air comes in through gaps around windows and doors, rising up through chimneys or cold air vents, while warm air escapes. Obviously, your heating system pushes warm air around your home, but if it keeps escaping outside and cold air is coming in to replace it, you aren’t heating your home, you’re heating the outside.
Radiation is heat transferring through electromagnetic energy waves. When you feel warm next to a radiator without being directly above it, that’s radiant heat. When you feel cold next to a single glazed window even when the air temperature in the room is comfortable, that’s radiant cold.
Heat loss through conduction, convection, and radiation happens at the same time in your home. The average annual gas consumption for UK households is over 11,000 kWh(BEIS). Most homes lose the greatest amount of heat through the roof, then walls, then floors, followed by windows and air leaks. The ratio changes based on your property type and age, but not the physics.
Most UK homes suffer from the homes we live in. We have millions of houses with solid walls dating back before cavity walls were standard. We have millions of ageing, single glazed windows. We have floors suspended above ventilated voids. We have roofs with barely any insulation. On average, less than half of homes have an EPC rating of C or higher (Energy Saving Trust). Don’t mistake size with impact though. Windows have a massive impact on how warm your home feels because of radiation.
Double glazing reduces heat loss through windows by approximately 50 percent over single glazing. Triple glazing improves on that by another 20 to 30 percent but at a much higher cost. For most homes in the UK, high quality double glazing with low emissivity coating and argon gas fills is ideal.
## Most Common Insulation Mistakes (That Waste Your Money)
Mistake #1: Starting insulation upgrades with your windows when you have major heat loss elsewhere. Windows let you see the warmth escape, making replacing them feel productive. However, they usually account for less than 15 percent of total heat loss. Think of the £8,000 you could save by not upgrading your windows and instead using that money for loft and wall insulation.
Mistake #2: Not installing your loft insulation to 270mm depth. Saving £100 to £200 on not installing 170mm instead of 270mm of insulation in your loft is a false economy. You still have to pay the installer to come out and do the work. You still can’t use your loft space. And your energy savings will be cut in half.
Mistake #3 : Ignoring gaps and thermal bridging. Heat stops transferring when it hits a gap. An uninsulated loft hatch will waste you £50 per year on extra heating costs. Thermal bridges, like cavity wall ties conducting heat through your insulation, can reduce your insulations effectiveness by up to 30 percent if not addressed.
Mistake #4: Having your cavity wall filled with insulation when you don’t have a cavity wall that can accept insulation. Some homes have exposed cavity walls which can’t accept insulation. Narrow cavities, poorly constructed cavities, and existing damp issues are also some things cavity wall installers tell you don’t matter when you should listen. In return, they leave your house with damp issues that cost more to fix.
Mistake #5: Obsessing over U-values without considering how well the insulation is installed. Good insulation materials installed badly will always perform worse than poorly insulated materials installed by a competent professional. DIY loft insulation is fine if you do it right. DIY cavity wall insulation is a disaster waiting to happen.
Mistake #6 : Thinking expensive insulation materials are always better. A lot of insulation materials have ‘eco-friendly’ labels that allow them to charge way over the odds. Sheep’s wool insulation can cost you 3 times more than mineral wool. But it won’t perform 3 times better. Natural insulation materials have their place, but they’re not always better.
## Insulation Research and Data Behind These Claims
The Energy Saving Trust monitors hundreds of retrofit project installations every year. Their data shows_INSTALLATION WHEN WE ASKED UNITS INSTALLED RECOMMENDED HEAT DEMANDReductions BEFORE AFTER Quality Assured Self Install Lofts 85% 85% 38% 38%Cavity Walls 78 78 37 37Solid Walls 83 83 37 37Roofs/Air leakage/Internal wall/ Floors *** 23%28% Of properties surveyed** Installations conducted by TrustMARK approved assessors and installers Data accurate as of August 2020 Heating demand reductions are based on predicted vs actual figures after one year.Unsurprisingly, when insulation retrofits are done properly and include loft, cavity wall, and internal wall insulation, average heat demand drops by 25 to 45 percent.
The Building Research Establishment also has performed studies on thousands of homes before and after insulation retrofits were completed. When you control for installer quality (all were competent tradespeople), BRE found that predicted savings go realised when the insulation work is performed correctly.
EHIC also provides data through the Energy Performance Certificate database. As the largest public dataset on real home energy performance in the UK, it’s unsurprising that properties with full insulation consistently heat less square metre of space while maintaining higher internal temperatures than similar properties without insulation. Annual energy bills are strongly correlated to the level of insulation in your home across property types and regions.
Several university research projects have taken BRE’s work further by not only measuring temperature and energy use but surveyed occupants on comfort and health impact. Keeping your home properly insulated improves comfort by maintaining even temperatures throughout the home. It also can reduce condensation issues and improve indoor air quality when paired with effective ventilation solutions.
## Typical Insulation Costs and Advice for Property Types
Victorian terrace houses: Solid walls and suspended timber floors are typical. Priorities are loft insulation, internal wall insulation, then floor insulation. Allow £6,000-£12,000 for a complete retrofit. External solid wall insulation requires Party Wall Agreements in some cases and always planning permission.
1930s semi-detached: Cavity walls that should be able to be filled, suspended floors, decent loft access. Get loft and cavity wall insulation first (£1500-£2500 for entire house), then floor insulation (£800-£1200). These homes offer the best return on insulation investment.
Post-war council house: Same as 1930s semi but might have solid concrete floors. Loft and cavity walls (£1200-£2000), then floor if you have suspended floors. Might have district heating which complicates matters.
Modern flats: Can’t do anything structurally to most flats but often have issues due to poor build quality. Upgrade windows if possible, address thermal bridges around balconies, and improve heating controls. Allow £2000-£5000 depending on size and problems.
Listed buildings: Restrictions on altering external appearance. Internal wall insulation, secondary glazing, loft insulation should all be allowed. You’ll need specialist quotes which will cost about 50 percent more than standard homes.
## Why Insulation Is Worth The Effort
If you’ve made it this far, you’re ready to insulate your home effectively. Start by getting an energy assessor out to your house to identify where you can make improvements and how much heating your home loses through different areas. You can always do insulation yourself, but questions are better answered by a professional who can tailor their advice to your homes specific problems.
Lower energy bills. Insulation will save you money on your energy bills. A lot of money. Expect reductions of £300 to £600 per year on an average home. Oversimplified payback period is 5-15 years depending on measures installed and current energy prices.
Feeling warmer. Properly insulated homes feel warmer quicker and stay warmer longer. Even if you don’t touch your thermostat, your home will feel warmer because you’ve eliminated many of the cold radiators and windows.
Reduce bills variability. Insulated homes heat more evenly and stay at a constant temperature with minimal heating input. That means your energy bills are much more predictable because heat loss is minimised. Compare this to a drafty house that requires constant heating to keep the same temperature.
Improved indoor air quality. Reduced condensation and more consistent temperatures mean better indoor air quality. Cold surfaces inside your home aid condensation. Insulation and upgraded windows eliminate those cold surfaces.
Increased property value. Buyers are becoming more savvy to high energy bills. Well insulated homes sell faster and for more money. Comprehensive insulation upgrades should add more value than they cost.
Less carbon. Save the planet by keeping your heat inside your home. Insulated homes produce between 1.5 and 2.5 tonnes less CO2 per year than a similar uninsulated home. Over the lifetime of that insulation thats a huge difference.
Healthy homes. Everyone feels better in a warm house. From lower rates of respiratory problems to better sleep and less stress over high energy bills, your whole family will benefit from a properly insulated home. Helpful for elderly, children, or those with pre-existing conditions.
## Wrap Up: Improve Heat Efficiency Step-by-Step (On A Budget)
Step 1: Assessment and Planning (1-2 weeks)
Order an Energy Performance Certificate if you haven’t had one done recently. Ideally get a detailed energy assessment conducted that tells you where your heat loss is greatest. Physically walk through your home on a cold day and identify where you can feel draughts coming from. Look for cold spots on walls, or areas where the inside of your external walls are cold to touch.
Look for existing insulation. Most homes have some loft insulation, but rarely enough. Cavity walls maybe filled, maybe not. Floors are rarely insulated so treat as uninsulated until you know otherwise. Note any areas that may cause installation issues like access, asbestos, electrical installations etc.
Budget: £60-120 for EPC and detailed survey
Step 2 Loft insulation (1 week)
As mentioned earlier, the first port of call should always be your loft. Its easiest to access and gives you the biggest bang for your buck. DIY if you want, but buy your materials from a trade supplier instead of B&Q. Wear breathing protection and lay boarding down if you have to walk on your joists. Don’t cut corners or skimp time here.
Ensure complete coverage with no gaps. Remember heat conducts around your joists if you don’t install your insulation correctly.
Step 3 Wall insulation (2-4 weeks)
Cavity wall is simple. Get three quotes from different installers. Check they are registered with the Cavity Insulation Guarantee Agency(CIGA). Anyone who comes knocking on your door saying you need insulation and can do it immediately is a cowboy. CIGA approved installers will professionally survey your property, check for existing damp and turn away if your house isn’t suitable.
Solid wall insulation is a whole other job and often needs planning permission. Get quotes from several companies that can offer you advice specific to your house. You might want to wait until you are doing other renovation work and spread the cost.
Step 4 Floors/windows (1-4 weeks)
Floor insulation is amazing if you have suspended timber floors and can ignore otherwise. Allows for loft living conditions without the crippling heat loss through your floor. If you have solid floors it’s either going to cost a fortune or invasive. Another job for when renovating.
Upgrade windows by draught proofing existing windows (£50-£150), adding secondary glazing where possible before committing to full replacements. Double glazed windows cost £5,000-£15,000+ to replace throughout your entire home. Start at the cheap end of those options.
Step 5 Go back to step 1 and do it all again.
Monitor your energy use going forward to ensure you are seeing the savings you were expecting. It can take a full heating season to get an accurate picture. You will notice improved comfort right away though and lower energy bills within the first couple of months.
Don’t forget about heating controls if you haven’t already. Upgrade thermostats, services with TRVs, and install insulation boards behind your radiators on external walls. Once you’ve slowed heat loss as much as possible its time to make sure youre using it efficiently.
Originally published March 1, 2020. Last updated October 21, 2020.<|end_of_document|>
