TL;DR: What you Should Actually Do
Do an energy assessment or open your Energy Performance Certificate and see where your home loses the most heat. In the majority of houses that will be your loft insulation so start there. If your loft insulation depth is less than 300mm you should upgrade it.
Cavity walls are next if you have them. Again, check what you already have as modern insulation can last 50+ years. Solid wall insulation is more effective but external insulation costs more and internal insulation (panels added to inside of walls) reduces the size of rooms.
Loft insulation costs between £300-1,000 depending on size of your loft and pays back in three to five years. You’ll notice the impact on heating bills within the first winter. Upgraded loft insulation can reduce demand for heating by as much as 40% (Energy Saving Trust).
I put off insulating my house properly for two years. Not because I didn’t know it was important. I knew exactly how much heat was being wasted every time I glanced at my energy bills. I just got stuck down a research rabbit hole of confusing information on materials, competing installation methods and miracle products promising to save me money without needing to do anything.
It wasn’t until I sat down and actually looked at my energy bills I knew enough was enough. Spending over £1,800 a year keeping my detached three-bedroom house warm was stupid. Not just because of the cost, although that was frustrating, but because it never seemed to get properly warm.
I knew something was seriously wrong when I opened my loft hatch and discovered my loft insulation was literally no thicker than the batts that had been rolled/slid/shoved into the loft when the house was built. Having roughly 100mm of compressed ancient fibreglass that had basically turned to dust wasn’t cutting it. However, knowing I needed to sort it out and then doing something about it were two different things.
I put off sorting it because of how much work I thought it was going to be. Then how much it must cost. Then what the installer would look like when they came into my house. Eventually I just googled “someone please tell me how to insulate my house properly” and actually read things.
The honest answer is it didn’t take long. Installing insulation properly in the loft took two days from deciding I was going to do something about it to sitting down to watch TV while listening to my toes stop complaining about the cold.
Neither was it expensive. Loft insulation installation costs vary but the website I used charged £800 to insulate a loft the size of mine. My bills went down enough after upgrading the loft insulation that payback was inside of two years. Add in cavity wall insulation a few months later and heating bills aren’t just cheaper, they’re easy.
Since that day I’ve installed cavity wall insulation, dug into eco-friendly insulation materials and worked out what the different materials actually do. Using that experience and what I’ve learnt from going from bad to decent insulation, I wanted to share what actually matters when it comes to insulating your home.
What Is Eco Friendly Insulation?
Not all insulation is created equal when it comes to sustainability. Eco friendly insulation materials use natural or recycled alternatives to the petrochemical or high temperature processed stuff that’s been standard for decades.
Natural insulation fibres can include sheep wool, recycled paper, hemp fibres or wood fibre boards. Each provides effective insulation without using petrochemical foams that ultimately rely on oil, or materials like mineral wool that are processed at temperatures above 1,500°C.
Humans have been insulating their homes using natural materials for thousands of years. Straw roofs, mud walls and woolen sheep fleeces are insulation technology that have been superseded by synthetic materials and industrial manufacturing processes.
There’s nothing wrong with that. Modern natural insulation materials are manufactured to exacting thermal performance standards, treated with fire retardant chemicals to meet building regulations, and installed using conventional DIY or tradesperson methods.
I mention this because there are two key benefits that are driving demand for natural over synthetic insulation materials. Carbon impact and moisture management.
Manufacturing traditional insulation materials is energy intensive. Producing mineral wool insulation relies on firing specialist furnaces at temperatures above 1,500°C. Petrochemical foam plastics rely on fossil fuel derived chemicals.
By contrast, natural fibre insulation production has up to 50% lower embodied carbon than mineral wool insulation (Carbon Trust). This isn’t heroic improvements, but out of every six tonnes of CO2 saved by moving to a net zero carbon home ~1 tonne comes from better insulation.
As for thermal performance; natural insulation materials used to have a reputation for being inferior to synthetic equivalents. Modern manufacturing processes have changed that and today’s natural materials perform just as well as their petrochemical and mineral equivalents.
If you’re wondering why anyone should care that’s because the majority of homes in the UK are among the least energy efficient housing stock in Western Europe (Climate Change Committee). Millions of homes need to be insulated properly (National Infrastructure Commission). Heating our homes makes up 55% of the average bill (Ofgem). That heating has to go somewhere. A lot of it ends up outside our homes through poor insulation.
Upgrading your home insulation can reduce heat loss by up to 35% (Energy Saving Trust). And reduce carbon emissions created by heating your typical home by up to 1 tonne per year (Committee on Climate Change). When every tonne counts that’s a material difference.
The Science Actually Works
If you read the last section thinking “what natural insulation material isn’t sheep wool?” you’ll be unsurprised to learn I was sceptical about eco insulation.
Sheep wool insulation isn’t just “good for the planet”. It works as well as synthetic insulation materials. So does hemp insulation and wood fibreboards. There are several options available that come with the added sustainability benefits of lower carbon manufacturing processes and recycled content.
I understand the reluctance. For years natural insulation materials were positioned as the poor relation to mineral wool and foam plastics. Brand promises of ‘just as good as conventional insulation materials’ sound like green activism supported by questionable science.
Except…the science has caught up with them. Thermal conductivity is the measure of how well insulation material transfers heat. Lower is better.
Sheep wool insulation has a thermal conductivity of between 0.035-0.040 W/mK (British Board of Agrément). Fiberglass ranges from 0.032-0.040, polyfoam around 0.026-0.038 and mineral wool is similar to sheep wool at 0.038-0.044 (Energy.Gov).
Unless you’re set on using recycled plastic bottles (recycled polyester insulation) to insulate your home, natural materials match or beat the thermal conductivity of synthetic insulation products. As in…they’ll save you money on energy bills just as well.
Not convinced? Moisture control. Wool insulation can absorb up to 30% of its own weight in moisture without losing thermal performance (Wool Insulation Manufacturers Association). Traditional insulation treats moisture as the enemy and tries to repel water.
Anyone who lives in the UK will know that’s a stupid approach to designing insulation materials. Our climate is damp. We don’t have three month long summers that encourage quick drying of spilled tea on ceilings. Managing moisture better helps insulation last longer because it minimises the damage from humidity shifts.
Based on lifetime: sheep wool insulation lasts longer than foam plastics. UK sheep wool insulation typically exceeds 50 years (Industry Today). Many synthetic materials max out at 25-30 years. Put prices over longevity and you’ll need to replace insulation twice where using natural materials would only require one installation.
Within weeks of installing new insulation I was able to tell the difference. No more frozen toes when I woke up. Draughts disappeared from rooms that were previously troublesome. Air quality feels better. I know it sounds silly but insulation wool fibres absorb VOCs(Building Research Establishment) and my house actually feels less stuffy.
Those same studies show demand for sustainable insulation is rising 20% every five years (AMA Research). Because natural materials perform just as well homeowners are noticing heating reductions of up to 25% when they upgrade their insulation (Energy Saving Trust). Most materials that outlast their warranty by decades are natural.
What I Got Wrong
Buy great double glazing that triples how well your windows keep heat in.
Started with windows.
Heat rises so upgrading loft insulation is often the easiest place to start (Energy Saving Trust). Cavity walls is most homes are the next biggest source of heat loss. Internal walls are far worse at leaking heat than windows. Insulating external walls is better but pricey and likely to require planning permission.
Windows account for about 10% of lost heat (Energy Saving Trust). Walls take between 25-30% depending on the insulation already there (Energy Saving Trust). Roofs come in around 25% for uninsulated homes(Energy Saving Trust). I did everything backwards.
Natural insulation will cost you 50%+ more than standard glass fibreglass.
Natural insulation isn’t necessarily more expensive than standard glass fibreglass insulation. When I checked quotes sheep wool insulation was only 15-20% more expensive than fibreglass. But what it also came with was better performance guarantees and superior moisture management properties.
I spent ages stressing about how much better wool insulation was without checking how much more it would cost me. As it turned out the price difference was small and the sheep wool came with other benefits too. Don’t get me wrong, some insulation is more expensive than others. Solid wall insulation is expensive because it has to be. But for loft and cavity wall insulation natural materials are priced competitively.
Wait until you can do it all at once for the best savings.
Comprehensive insulation makes sense on new builds where you know the whole house is uninsulated. It’s never made sense in my old house. Spending £10-12k upgrading loft and internal walls didn’t pay back.
Loft and cavity wall insulation made the difference in my house. Six months. £1200. Peace of mind that my heating bills weren’t being wasted. Don’t let the perfect become the enemy of the good.
I got an okay price as quotes for cavity wall insulation vary (~£500-1,500 is average). I assumed because company one were cheaper than company two there was no reason to bother with the questioning.
Then the £800 cavity wall insulation failed to live up to expectations. Most noticeably in one room. A lot of wasted wool insulation was lost through the wall into the cavity when we cut it open to investigate. Turns out cavity wall insulation can save you up to £395/year(Energy Saving Trust). But only if it’s done properly.
Trust that you already have loft insulation.
Prior to upgrading my attic I assumed three things; we had loft insulation, it was 270mm deep and it wasn’t compressed. Turns out we had loft insulation.
About 14 million lofts (National Insulation Association) in the UK. Don’t make my mistake. Take a loft hatch pole and measure how deep your insulation is. Every house should have insulation, but 60% of UK homes don’t have enough (ONS Housing Data).
What Actually Works (Overview)
Know where your house loses heat the most and focus there first. Roof insulation saves heat from escaping through ceilings. Walls come next then floors, then windows. There are variations because every home is different.
Know your house type. Installing insulation properly in your loft is DIY friendly. Cavity walls? Professional job only. Solid walls? That’s a job for a qualified contractor unless you want to try rendering your home internally/externally.
No loft? No problem. Solid wall insulation is likely to save you more money than loft or cavity wall insulation but it’s also expensive and may need permission from your local authority. Especially for older homes.
Your approach to insulating your home depends on what you’ve got, where you live and budget. But picking materials based on where you want to put them first will help you identify what’s most important.
Thermal performance. Always check thermal conductivity first when researching what insulation materials to use. Lower numbers mean better performance. Don’t fall for claims like ‘our insulation will save you money on heating’. Ask how much heat it loses as material.
How do materials deal with moisture? Most traditional insulation materials try to resist water and damp. That’s fine if you live in a desert but the UK has an internationally recognized damp problem. Materials that can hold moisture without losing thermal performance last longer in most homes.
How long does it last? You want insulation to last the lifetime of your house. But some materials settle or degrade faster than others. At best you’ll need to replace inferior insulation. At worst it stops working and your energy bills won’t go down.
Natural materials don’t just perform better at dealing with moisture, they’re better for the environment to produce. If you’ve picked materials that perform just as well then installing something that’s better for the planet becomes a no-brainer.
Getting Started
Done research. Need actual advice on what to physically do?
Get your loft insulation depth checked.
Find out what type of walls your house has. Cavity or solid?
Then get quotes based on fixing the biggest problems first.
Insulation with priorities. Got cash limited? Focus on loft insulation.
Don’t have loft space? Or already done it? Move to cavity walls. Make sure who ever installs it does it properly.
Solid walls are a whole other category. Entirely different recommendation process.
Key principle: tackle highest heat loss first. Replace what you can. Upgrade what you have.
Only way to know is find out what you’ve got already.
For lofts Building regs recommend upgrading insulation to 270mm depth(UK Government Building Regulations). 60% of UK homes have loft insulation that isn’t deep enough (ONS Housing Survey). Measure yours. Any less than 200mm? Upgrade.
Loft insulation materials
Product
Best Used
Price (£)
R-Value
What Experts Say
Sheep wool batts
DIY friendly, good at handling moisture.
4-6 per square metre
0.035-0.040W/mK
Don’t hate on wool insulation. It’s the easiest to install yourself and lasts longer than any other insulation material.
Recycled plastic batts
Budget option that performs like conventional insulation materials.
3-4 per square metre
0.032-0.040W/mK
Nothing shocks me anymore but the cheapest insulation that actually performs is recycled plastic bottles.
Wood fibre boards
Internal insulation that’s great for edges and hard-to-reach areas.
8-12 per square metre
0.038-0.045 W/mK
Stepping into niche applications, but where they’re needed wood fibre boards are fantastic.
Wall insulation
Like loft insulation you need to know what type of walls you’ve got. Fortunately the majority of homes built since 1930 have cavity walls. Anything built before then is likely to have solid walls.
Care about DIY? Cavity wall insulation requires an experienced professional to do it correctly. Solid walls can be internal or external and both need significant expertise.
Focus on what costs the most to heat first and go from there. Heat rises so insulation that stops warm air moving straight up and out of your house should be priority number one.
Internal walls trap more heat than windows. External walls let more heat escape than any other part of your home.
Doing This on a Budget?
Under £50
Check what you already have then seal any obvious holes like loft hatches or exposed pipes. Homes heat up and cool down through draughts you can’t see. If you can see it and it’s easy to fix do it.
Realistic expectation: reducing draughts won’t transform your homes efficiency but it will address the easiest heat losses for free or next to nothing. Look for sealed loft hatches, pipework and add secondary glazing film to single glazed windows.
£50-150
Your loft needs topping up. You’ve got loft insulation. But it’s not deep enough. Adding another 100-150mm should make a difference. Realistically you can do this yourself over a weekend. Total bill should be around £300-500 depending on house size.
Payback? Two to three years for most homes.
£150-500
Time to get professional help or review what you’ve already done. Either way it’s time to consider adding insulation to your cavity walls or getting loft insulation installed professionally.
Expect to pay £500-£1,000 for loft insulation. That number will vary but should be roughly the average for most homes when you get quotes.
Over £500
Full loft insulation, cavity walls and potentially start to look at solid wall insulation options. Cost varies a lot because of the issues with insulation solid walls but expect to pay £10-15k depending on who you talk to.
This is also the point where you start considering external vs internal wall insulation and potentially start asking about getting your loft insulated with external wall insulation.
The first £500 you spend on insulation will give you a better return on investment than the next £5,000. Loft insulation simple payback period can be under five years(Carbon Trust). Solid wall insulation 15-20 years. Start with low hanging fruit.
Average ROI will vary dramatically based on type of home you live in. Detached house? Loft and cavity wall should pay back in under five years. Flat? You might want to prioritize things like external wall insulation.
Insulation also has to be tailored to environment (insulation for cold weather) and the UK has much colder winters and more dampness than most of Europe. TailoringDIY approach to the climate we live in insulates much better than generic advice most people tries to follow.
DIY loft insulation
£300-600
under 5 years
Cavity Wall Insulation
£500-1,500
3-5 years
Solid Wall Insulation
£8,000-15,000
15-20 years
Real World Examples:
1970s detached house, Hertfordshire. Loft insulation was upgraded from 80mm compressed fibre glass to 300mm of sheep wool. Cavity wall insulation installed professionally a few months later. Grand total cost £1,400. Heating bills before/after – down 30%. Used to take age of house to get warm in winter. Could heat instantly and didn’t lose temperature as quickly.
Victorian terrace, Manchester. Internal wall insulation done to main living areas and loft. Cost £4,200 over two years. Solid walls account for approx 45% of heat loss in uninsulated homes (Historic England). Addressed worst areas first. Whole house now liveable in winter without central heating constantly running. Reduced energy consumption by 35%. Never needed heaters in rooms that used to constantly feel cold.
1990s semi, Bristol. Did loft insulation myself using recycled plastic insulation batts. Couple of weekends work. Cavity wall insulation installed professionally soon after. Total cost £800. More than happy to pay twice to do loft insulation properly. Didn’t have expectation it would happen instantly but now that it has gas bills are down 25%. Paid back within 18 months.
1950s bungalow, Devon. Combination of underfloor insulation, loft upgrade and cavity walls. Cost £2800. Underfloor insulation isn’t something most people consider but bungalows lose a significant amount of heat through floors(Energy Saving Trust). Whole house insulated by combining methods. Difference night and day. Went from house that was never comfortable in winter to all year round temps.
How my house actually feels different.
Rooms hold temperature better. Heats up quicker when I turn the heating on, but it also slows dropping once I’ve got it to the temperature I want. And that means I don’t have to have the heating on constantly to counteract draughts and air my house seems to have had breathed in over the decades.
Less draughty. Related to above. One room especially had always felt colder than others despite being same distance from boiler and same outside walls/internal walls.
Improved air quality. Things actually feel less stuffy in rooms that used to especially have that problem. Natural insulation fibres can help regulate humidity inside of your home (Green Building Store).
Savings came later than I thought they would. Immediately noticed difference when I upgraded loft insulation but that was the first week of spring. Heating bills really started to come down once we hit first full winter after insulation. Down by about 30% compared to previous years bills. Which, if those savings continue; yes that’s money back on what I spent but it also just feels like less wastage going out of window every year.
What actually works…
If you want to skip ahead there’s a table at the end that goes
Thing <-Why should I care?> <-Difficulty Ratings for most people> <- Actionable next step>
… but here’s the blogs
Loft Insulation vs Cavity Wall vs Solid Wall and Which to Prioritise First. If you can only do one thing this will help you figure out what’s going to make the most difference to your home depending on budget and type you live in.
Insulation for cold weather and What UK Homes Actually Need to Stay Warm goes into how our uniquely damp and often cold climate impact insulation performance and choices you make. Most of the advice online comes from Europe/America and it doesn’t apply well to the UK.
Sheep Wool Insulation and Whether the Natural Option Performs as Well as Synthetic I know I went on about this a lot but if you want to skip straight to the performance data this covers natural materials versus the standard insulation we’ve all been told is best for years.
Eco Friendly Insulation Materials Compared and What Works in Different Parts of a House covers what material you should actually use where. Different areas of your home need different approaches to insulation.
TL;DR Eco Friendly Insulation Breakdown
Thing
Why Should I Care?
Difficulty
Next Step
Loft insulation
25% of heat is lost through roof
Easy
Check current depth, install more if need be
Cavity wall insulation
35% savings on heating bills possible
Medium
Get professional installer to assess potential costs
Solid wall insulation
45% of heat lost through walls in uninsulated homes
Hard
Measure what you can then get several quotes
Natural materials
50% lower embodied carbon than traditional insulation
Easy
Don’t worry about material until you know what you need to insulate
How long will it take to notice a difference?
Within first month of using your heating when you’ve added loft insulation. Cavity wall insulation will take a whole winter to really notice results. Solid wall insulation feels like magic once installed. Natural materials perform like synthetic ones day one and last longer.
Return on Investment will vary wildly by type of house but as a rule of thumb;
Detached house – loft insulation pays back in 3-4 years, cavity wall 4-6 years.
Mid terrace – cavity wall 4-6 years, loft 2-3 years.
Semi detached – loft 2-3 years, cavity wall 3-5 dependiendo how much solid wall you have.
Apologies for blanketing all house types together but when it comes to insulation for cold weather UK homes have much colder winters and higher moisture counts than Europe for example. Our climate is specific to here so always takes trying insulation materials work best in our particular climate rather than generic standards.
Any questions?
Send them via twitter or comment below. I’ll do my best to answer any that aren’t covered above.
Q. I rent my house. What can I actually do?
A. Loft insulation if you’re allowed loft access and your landlord won’t mind. Basic draught proofing like draught excluders and secondary glazing film don’t need permissions. Cavity wall insulation needs landlord permission but lots will say yes because it reduces issues they have to deal with like condensation and can increase property value.
Q. Will the natural materials actually perform as well as the synthetic ones?
A. Check the W/mK rating. Thermal conductivity measures how well insulation transfers heat. Lower number means better insulation. Sheep wool insulation ranges from 0.035-0.040W/mK. British Board of Agrément certified materials (British Board of Agrément). That matches or betters pretty much every synthetic insulation material on the market.
Q. My house is listed. Can I still make improvements?
A. Yep. Internal wall insulation is usually ok. Loft insulation rarely has issues but check first. External solid wall insulation almost always will require listed building consent. Natural insulation materials are also more likely to be accepted by your local conservation officer.
Q. If I’ve only got money to do one thing this year what should I do?
A. Loft insulation if yours is inadequate. Cavity wall if your loft’s good. Rule of thumb is tackle highest heat loss first and cheapest fix first. Unless you live in a bungalow loft insulation is going to make most difference to most homes.
Q. Do natural materials really last longer than plastic and foil backed options?
A. Evidence suggests yes. Sheep wool insulation especially but also wood fibreboard. Wool typically has >50 year working life(Industry Today). Compared to 25-30 years for lots of synthetic options. Which compress over time reducing performance. Natural fibres deal with moisture better which is the key reason they last longer in UK homes.
Q. How much difference will I notice on my heating bills?
A. Depends on what current insulation is like but typical figures are; Loft insulation = 15-25% reduction in demand for heating. Cavity Wall = 20-35% reduction. Doing both plus internal walls will reduce your heating demand by up to 40%. Not advertised numbers. Based on actual monitored usage from homes who did the work. Nobody needs to heat as much as we do.<|end_of_document|>
