Our new place (built 1975) has no cavity wall insulation, and precious little roof insulation either.

We've had various bits of advice suggesting we:
a) Do it ourselves
b) Don't do it ourselves and get a grant for it via a company who does that sort of thing (i.e., pay them a bit and they sort out a grant)
c) Get our utility company to do it as it's very cheap with them (is this cos of the grant thing?)
d) Wear more clothes and hug each other.

Any glowing insights on ease of fitting/options I may have missed? How much would I realistically expect to save each month?

Thanks!

R

Loft ins is easy and we got tons for £100 from B&Q.

Re the Cavity Wall Insulation, get your house check properly as to whether it suits having CWI, as some house need the air flow to keep it dry.

Insulation has the quickest payback of any energy saving technology. By a country mile.

Have a google for the uk-diy faq on it.

Mega insulate the loft as much as you can. More than 300mm quilted making sure there is a reflective side, if any, facing down (though I'm not sure how effective this actually is). If you still feel you want more then you can use issulated plaster board on the walls. you lose a bit of floor space but it maintains the Cavity Wall gap, probably only 50mm. I don't really believe in CWI as CW's are designed to have air flow/seperation between outer and inner.

Loft insulation is easy enough to do yourself, plenty of guides online. If you call the Energy Saving Trust on 0800 512 012 then they can tell you if there are any subsidised insulation schemes in your area, they're usually targeted at the elderly etc but you never know.

Latest savings from memory are around £350 per year (based on a 3 bed semi with family use I think) for loft and CWI. You should really notice a difference with it done.

If you do super insulate your loft just make sure that you have good cross loft space ventilation to avoid possible condensation issues.

Cavity wall insulation needs to be done by an "approved installer", make sure that your cavites are surevyed for it first & it also depends on your location (exposure) external wall type (brick certain pointing types)

Loft insulation then your heating source may give more bangs for your bucks.

We've just had cavity wall insulation done in our 1930's semi. £149 through npower (our supplier). We were told energy companies have to subsidise these things under government rules. Thats why b and q keep doing cheap loft insulation. Thats underwritten by british gas apparently. Ring your energy company and see if they can help,
Graham

We're apparently with British Gas for energy but their prices for insulation seem to be a fair bit more than the likes of eon. The house is a "cold" house, which may be partly due to the orientation of the main rooms we use, but with a 2 week old nipper I'd rather just keep the temp a little higher than at present.

Is DIY loft stuff as easy as just getting up there and wanging the stuff down?

Our local authority last year had a pot of money and offered cavity wall insulation to anyone in the borough. Wasn't means tested, but also was not greatly publicised either, so it might be worth seeing if your LA has anything simialr on the go. Majority of people on our estate got their houses done, we noticed a big improvement, and usually we find our gas bills going into negative territory, but this winter we've stayed in credit – having decent double glazing fitted has also helped considerably though!

Our loft/attic still needs better insulation than from new, but over the yeasr we've accumulated that much junk in there that I can't face up to doing the job currently!

Lay it yourself in the attic- you *will* do a better job than any of the insulation trades. Lay it deep, lay it carefully and snug up with no gaps, and leave ventilation over and around edges of roof. Buy good stuff, usually buy one get one free from B&Q, and at least 300mm deep *will* be worth it. For cavity, get an installer subsidised by local council or energy company.
If you have solid walls, speak to Natural Building Technologies.

Alongside this, draft proof and draft proof, insulate the floor (again, cheap and simple), and get some good heavy curtains hung with good double glazing.

Make sure you layer it well ie fill the ceiling rafters with 100mm insulation then another 200-250mm perpendicular to the rafters

If you can DIY then do it, it will be well cheaper than using a utility. Even the £250 (ish) they charge is subsidised as there are call centres, surveyors and fitters involved in the process ramping up the cost considerably. I think the B&Q stuff is subsidised by us too as we have to shift a certain amount of it or we get fined 10% of turnover

Don't forget to insulate your cold water tank and pipes if you are doing your loft, otherwise they will freeze in winter.

+1 for advice from matt_outandabout

Doing the loft yourself is easy. Just wear gloves and long sleeves if you're using glass fibre rolls. And make sure that you shift the wiring for lighting to the cold side (there should be enough slack to do this). Also its important that the loft hatch is well draft proofed as well.

Cavity walls are a bit harder. Fine for some properties, not so good for others. Depends on brick porosity, mortar type, exposure of the house. Might be worth finding out if your neighbours have had it done and if they've had any probs. I wouldn't trust the advice of a cavity wall insulation fitting company on this one… Having said that my mate had his done and it works really really well, with a noticeable increase in temperature, i.e. much more comfortable house.

Energy suppliers are obliged through CERT to reduce set quotas of CO2 through insulation measures.

This website might be useful.

Philby – Member
Don't forget to insulate your cold water tank and pipes if you are doing your loft, otherwise they will freeze in winter.

Glad someone posted this 😆

Dad had his done last year, toilet ceiling came down over winter due to overflow pipe freezing, so do that to. Luckily it is a wet room for mum. Although any drips will freeze and acumulate, so before winter sets in make sure overflow is not dripping.

Thanks for all the advice folks! Will crack on with it before the missus starts to fill the loft space with tons of baby stuff… Some very interesting things about cavity wall insulation as well. There's one bit of the house (East Wing) which will need something as it's 100% in shade, big windows either end, 1 rad, etc so I will monitor temperature and do a before and after post in due course…

A saving of 350 a year?? I very much doubt that!!

Got the walls done last year. It makes a big difference. Year before it was cold in our house. This year toasty, and we had some cold days. Got it done for £150 through our gas supplier. It took them a couple of hours and they didn't even nead to come in the house. They used the carbon polystyrene balls. No problems with damp yet – I'm not sure how there would be tbh.

Haven't got round to the loft yet but I'd do that myself. You can get it done by someone for £150 or so but that does not include empying all the crap out of the loft and boarding out a section after it. So might as well do it myself.

Matt_oab, or anyone for that matter – I have often wondered: If you draught-proof your house to the max, will there be insufficient air circulation to provide fresh air for breathing?

I heard somewhere that air quality was poor in very well insulated houses.

Molgrips. We now have to pressure test all new houses to a certain level. We even go to the legnths of sealing round floor joists as they enter bearing Walls and sealing any cable holes that go through stud Walls up into the roof space! And then all fans in bathrooms etc have to be taped up, even the bloody letter box is sealed. Pressurise the house, if it fails, no building control certificate !! Load of bollox!!

Matt_oab, or anyone for that matter – I have often wondered: If you draught-proof your house to the max, will there be insufficient air circulation to provide fresh air for breathing?

In theory, if you seal up the house airtight, then yes moisture will not be able to escape and you could get build up of stale air, even C02. In practice, in an old house you could NOT seal it up this tight. You may be able to improve the uncontrolled infiltration, but not stop it. Typically an old house may be 20-30+ ach.
.
wrightyson – you do need airtightness – and way better than the 10 ach that UK regs require. 'Build tight, ventilate right' – so on the continent they build far more airtight buildings, but they ALL have heat recovering ventilation units fitted. We were building houses with sub 3 ach regularly, but it is/was/will be a battle with UK building systems to get below 10 ach – and questionable due to moisture issues whether you want to without ventilation. Bear in mind that a properly insulated house will lose more heat through uncontrolled infiltration than the walls – so shy bother with all this insulation / double glazing efficient boilers etc if you are not going to seal the drafts (the uncontrolled infiltration)?

We have a new house tho matt… If I go about sealing it up like mad, am I risking a problem? Already pretty stuffy at nights sometimes, even in winter.

For that matter, can I get one of these heat-recovering ventilation systems?

As the others said but be very wary of cavity wall insulation. The cavity has already got the best insulator there is in there, air. As long as it's not moving around too much it's a good insulatror and completely watertight. If it is moving around alot chances are it's meant to as there will be airbricks etc. in the wall. A lot of people have had issues with damp penetration after having cavity wall insulation. That makes a cold house seem like a good option. None of the cavity wall fillers are waterproof, sure the actual strands of glass fibre or polystyrene balls are waterproof but the water simply wicks between them to reach the inner wall. Even the expanding foam is far from water tight. Plus if you end up with a patchy fill you can get cold spots that tend to attract condensation which will also cause damp problems. When new houses are built they have special cavity wall insulation inserted which is tied to the inner wall still leaving a small cavity for the water to run down. In fact the cavity was first seen on western properties in the British Isles as a waterproofing technique. If you have porous bricks (like I have) and are exposed to the wind (again like my house) the water can literally stream through the bricks. My garage is only one layer of bricks deep, when we first moved in if you put your hand flat on the wall in a storm with the wind behind the rain water would run over the back of your hand. I had to cover the whole internal surface with plastic damp proof sheeting to make the garage watertight.

Not surprisingly the installation companies don't make a big issue of it and it's an easy and relatively cheap way for the government to look like it's doing something green.

The cavity has already got the best insulator there is in there, air

Mate, get it right. STILL air is a GOOD insulator. The best insulator is nothing, I believe a Mr Thermos figured that out. In a cavity wall, there's plenty of room for convection and air currents to transfer heat around, hence cavity wall insulation.

However, I am not arguing with your points about damp 🙂

Btw, the inner wall of my house is made of thermolite blocks and is rendered with something grey behind the drywall. What is it, and why is it there?

I believe a Mr Thermos figured that out.

Mr Dewar actually.

@ Matt O, We may be putting full heat recovery in our latest build. I've been building factory units for over 10 years now and we've always go round the pressure test area of them by claiming is as an unheated space. Ie heaters ate there purely for frost protection! As the arse end has fell out of that Market gone into a little bit of housing development for now. Any tips on improving the test figures?

@Molgrips. Thermolites are a great insulator in themselves and are used to get high enough insulation values. I'd be very surprised if they rendered the Walls first and then went onto dot and dab as well unless you're in
a very high end development. I suppose that way of doing things could help with sound insulation. Are you sure it's not just one of the dabs behind the plasterboard. Oh and for that matter, dot and dab systems are also used because they again improve insulation by having the small air pockets between block and board!

Ask Jeff – this guy writes a weekly property advice column for the Telegraph:

http://www.askjeff.co.uk/cavity.html

I think he also advises against excessive loft insulation as it can cause condensation in the loft space unless it is well ventilated.

I believe a Mr Thermos figured that out.

Mr Dewar actually.

Yes, clearly that was a joke. Thermos is obviously a brand name playing on the word 'thermal'. I'm not that dim 🙂

@wrightyson – I discovered this when concealing wires for my wall mounted telly. I ended up having to chop a section of plasterboard out, and you could clearly see some grey stuff slopped over the thermolite blocks. I had to chop a groove into it so I could fit more wires in the future without having to cut again.

Re draughts, our front door has a small gap at the bottom of it, and one of the upstairs patio doors (don't ask) also had a huge great gap around it when they built it, but we had them fix that. Also the extractor fans for the bathrooms are not sealed in any way 🙁

You were just probably unlucky and hit a line of dabs! When that shiit's gone off it's like bell metal! Oh and as for sealed fans in the bathrooms, I meant we have to seal them up before the test. ie plastic bag and gaffer tape so we don't lose the air through the ducting 😉

The cavity has already got the best insulator there is in there, air.

Do at least have a basic understanding of physics and thermal performance of walls before you make this statement….A cavity is there to try and prevent damp, it is generally accepted it is THE worst way to ruin any thermal performance in a wall.

Molgrips – you may have an issue, the only way to know is to get your house test results and see hos airtight it is. You can retrofit systems, but not as simple, and not as cheap, as when new.

The grey render stuff on the drywall these days is for airtigtness, as cracks in blocks /mortar are a cause of uncontrolled infiltration, and you CANNOT make dot n dabbbed boards airtight for long.

Moisture etc – we are getting into a whole world of stuff here, with mucho misleading information (from Kingspan etc) eg
http://www.natural-building.co.uk/PDF/Breathability-Matters-response-to-Kingspan.pdf

Airtightness help: http://www.natural-building.co.uk/news/2010/files/SIGA-Airtightness-manual.pdf

You were just probably unlucky and hit a line of dabs!

No, I did it between the dabs. It's different stuff. Grey, sort of cement like, and it doesn't touch the plasterboard.

Matt, thanks for the info, I will check out this kind of ventilation further. I already vaguely considered having some kind of circulation system to take hot air from the 2nd floor and pipe it down to the ground floor. Ground floor is always a little cold in the winter, 2nd floor always warm.

On the large sites theyre now pointing internal blockwork bothsides, cavity and face. I still can't believe it's a regular practice tho rendering and then dabbing! **** me that is just overkill!

Just side tracking a little… Currently in our loft there is only about 15 cm of old insulation. I want to board out the loft, but then there is no way I could get more insulation in as the gap between the rafters and the ceiling is only about 10cm. How can I add more insultation and still board out the loft, or is it one or the other?

Ta

Our house was built by Wimpey, but apparently was better made than many of the other houses in the area. It certainly looked better made then the Persimmon one we looked at, but we are not builders so don't know much 🙂

FunckyDunc – I put in a raised floor for boards, so have floorboards in addition to about 60cm of insulation.

How can I add more insultation and still board out the loft, or is it one or the other?

Either, build up the rafters somehow to suspend the boards so that you can fit another 150mm+ of insulation in soft batts in, OR, get a rigid board with reasonable compression strength, lay cheap OSB covering, then lay insulation boards over and then floor board (could be cheap OSB again) on top, but then do not over load.

On the large sites theyre now pointing internal blockwork bothsides, cavity and face. I still can't believe it's a regular practice tho rendering and then dabbing! **** me that is just overkill!

It has been normal on continental sites for decades, where cavities and block work are used. Time to leave behind our archaic and crap UK building systems and look to the continentals timberframe, or 'solid' walls and external insulation.

Matt as the yanks now there's a time and a place for timber frame! That won't be anywhere near, twister town, hurricane coast lines or for that matter those rather dry dusty places. When will they learn 🙂