Cold draughty roof

[JoceAndChris]

We must insulate this winter.

Does the stuff need to go between every joist, and does it need to go on the underside of the asphalt of the roof? How can I work out how much I need? Do I need to measure all the ceilings and calculate the area from that?

There are sections of the roof void we haven't visited and I can't go up there as I'm too scared, but Chris can, I hope. I certainly wouldn't want a tradesman walking around up there as it's a fragile structure of 200 year old reeds and timbers.

I have asthma so I'm thinking of something easy on the lungs. Any pointers in the right direction much appreciated, as ever.

 

[Flyfisher]

The usual approach is to just insulate above the ceilings, not the roof rafters. If you use the standard rockwool stuff then run one layer between the ceiling joists and then a second layer at right-angles.

I noticed that Jewson was advertising a "buy 1, get 3 free" deal when I visited my local branch a few weeks ago. (Just found this link: http://www.jewson.co.uk/en/templates/product/templateA.jsp?pageType=Product&itemId=prod350012). Click on the offer and it seems to lead to a calculator, which might be helpful even if you don't choose rockwool.

Of course there are various other insulation materials depending on your pocket and 'green' credentials.

If you have asthma then you'd be wise to let Chris install it, but make sure he wears a good mask. I favour FFP3 masks with a valve for easy breathing. One of those disposable overall suits can also be good for keeping all your skin covered so as not to become too itchy. It's not a bad time of year to be insulating ceilings because the temperatures are lower; crawling around in a cramped, dusty attic space is no fun at the best of times but is pretty much unbearable in the summer.

 

[MdB]

I noticed that Jewson was advertising a "buy 1, get 3 free" deal when I visited my local branch a few weeks ago. (Just found this link: http://www.jewson.co.uk/en/templates/pr ... prod350012). Click on the offer and it seems to lead to a calculator, which might be helpful even if you don't choose rockwool.

B and Q are £3 per roll at the moment. That will be hard to beat.

If you have asthma then you'd be wise to let Chris install it, but make sure he wears a good mask..

And washing up gloves with the ends taped to your sleeves. It looks stupid and gets very sweaty but helps stop the itching.

 

[JoceAndChris]

Many thanks for the advice. At that price (£3) it's absolute madness to burn another tank of oil with no insulation in the roof - not that we have our heating on yet.

The overalls, gloves etc sound like a pain but worth it. I think rather than doing each space at once (our loft void has distinct rooms, with walls) I should send poor old Chris into the furthest end this Sunday. We've done our wiring there so it needn't be touched. Some of the roof spaces still need rewiring and possibly hot water pipes bringing from the South to the North end of the building but I'd imagine you just lift this stuff up when you need to?

Off to look at the online calculator -thanks FF

 

[Feltwell]

If you don't want the itch of rockwool insulation, there are more "Chris friendly" alternatives, but not as cheap.

Sheep's wool based - I can't for the life of me think of the brand name, someone on here will know it - very green, very nice stuff to use

Recycled plastic bottle - B&Q sell this, it's fine, no itch. Doesn't fall apart as much as rockwool / fibreglass insulation.

Encapsulated insulation - basically fibreglass insulation wrapped in foil. OK, but still the itch factor when you have to cut it!

Regardless, if you have asthma I'd let someone else do the job. Whilst you can quite happily handle the sheepswool and plastic bottle insulation with no mask or gloves, you'll kick up lots of dust in your loft whatever you use so I'd still wear a mask.

 

[JoceAndChris]

Thanks so much for the overview of what can be used Feltwell, and some of the advantages and disadvantages of each - very useful. I think I'll let Chris decide as he's doing it.

I expect I'll be downstairs vacuuming, as dust just seems to love to sprinkle itself throughout!

 

[88v8]

You know of course that when you insulate it will make the roof spaces colder, so any pipes up there need to be well lagged beforehand, also the cold tank and any stop-cocks. Don't put insulation beneath the cold tank, the heat needs to get up there.
If the roof spaces are ventilated at the eaves, avoid blocking them with insulation.

Rockwool is fine, the itchiness is a good excuse for a long hot bath.

Ivor

 

[Penners]

overalls, gloves etc ...

...and goggles. Laying fibreglass/rockwool can give you terribly itchy, watery eyes. I tried the recycled plastic bottle stuff that Feltwell mentions, last time I needed to insulate. It's a hell of a lot less unpleasant to use.

And - just to re-emphasise what 88v8 has aid - if you're insulating between the attic floor joists (ie: above the bedroom ceilings) you must thoroughly insulate your cold water tank (not sure if you have one of those!) and any pipes which run above the insulation. Reducing heat loss through the attic increases the risk of a frozen pipe.

There's not much you can do about existing electric cables that will end up beneath the insulation, but if/when you have rewiring done, the new cables should run on top of the insulation.

Make sure you have a minimum insulation thickness of 270mm.

 

[AMc]

Make sure that your power cables are lifted up above the insulation. The resistance of a power cable under insulation increases which can lead to overheating and fires, especially on older wiring and if you're using high power appliances (fan heaters etc.).

The recommended depth is about 270mm or almost a foot of "wool" - going from none to that will save you a lot of oil and will make your house much nicer to be in.

Look at how you will get about up there once you've put that much insulation in. It's now a tricky job to work out where the joists are putting my reed ceilings in peril if I need to clamber about up there - doing it again I would screw blocks of wood to the tops of the joists and fix scaffold planks to those so there are safe routes to get around. That will also go down well with your electricians when you rewire.

When you come to rewire then it is simple to move the insulation out of the way but I would get Chris to do it. My sparks made a mess of the insulation, peeling back bits and tearing it and trampling it into the house - I should have scooped it all up and put it on the other side of the roof first then put it back when they'd gone.

 

[Pford75]

Depending on your buildings insurance, the work may also be notifiable.

You ought to check, because if Chris does have an accident and puts his foot through a ceiling, you want to be covered. Most insurers just require you to inform them when the work starts and when it is finished

 

[JoceAndChris]

Gosh, thanks for all the wonderful advice from the panel of experts! That's great. I don't think the tanks or pipes are insulated/ lagged at all so I guess that will be the first job. The cold water tank up there is massive, it's a thing of beauty actually, I reckon they must have built it in situ in the '30s. I'll need to read up on how to insulate tanks. The pipe lagging we're familiar with.

Pford - I'll ring NFU in that case then, many thanks.

AMc - I can't wait to see if the house feels warmer! I reckon we're spending about 3k a year on oil and electricity for heating - maybe more - and the house rarely feels warm in winter. Let's hope this will help, I'm sure it will.

Mr P - I think the plastic stuff does sound much better, and we'll use that.

It's a very good point about ease of walking about up there in the future. I hope Chris can do all the wiring though - and no wiring is old in this house as there was no electricity whatsoever until the late 80s.

I told Chris this morning about his forthcoming DIY job and he was less than thrilled, and said he didn't want to do it before draught-proofing some windows- but if I temptingly buy the stuff and pop it up by the attic doors he might be encouraged. Maybe the kind thing to do is to have a go at it myself, though I've got to admit I'm pretty scared of being in there with nobody around.

 

[Penners]

I'll need to read up on how to insulate tanks.

You can buy tank lagging kits, but they tend to be for standard sized tanks. Given the 'bespoke' nature of yours, I reckon your best bet is going to be to buy some batts of something like Kingspan, and simply cut them so as to form a 'box' around your tank. Obviously you'll need to cut holes for the pipes (including the the over-the-top expansion pipe if you have such a thing). You could assemble the box using good gaffer tape, or pin it together with meat skewers or the like. Make sure it's well assembled, without gaps.

Remember not to insulate underneath the tank. Heat leakage from the house below helps to prevent it from freezing.

 

[AMc]

AMc - I can't wait to see if the house feels warmer! I reckon we're spending about 3k a year on oil and electricity for heating - maybe more - and the house rarely feels warm in winter. Let's hope this will help, I'm sure it will.
snip
I told Chris this morning about his forthcoming DIY job and he was less than thrilled, and said he didn't want to do it before draught-proofing some windows- but if I temptingly buy the stuff and pop it up by the attic doors he might be encouraged. Maybe the kind thing to do is to have a go at it myself, though I've got to admit I'm pretty scared of being in there with nobody around.

It's not a tough job and involves very little skill, it just involves scrabbling around in the dirty loft. It will make a very big difference for a comparatively small outlay in money and time.
I have to admit I did it using normal "work" clothes, a cheap mask and gloves. With the proper gear (above) and perhaps a head torch it would have been easier and quicker but you should be able to insulate a large roof in a day.

The main trick is to get enough insulation to start with - it's surprising how much you need and how hard it can be to get it in the car. Get a generous amount, you can always lay the extra on top. Once you have it all in the house then install it in one go.

 

[MdB]

Make sure that your power cables are lifted up above the insulation.

Absolutely.

The resistance of a power cable under insulation increases

Sorry, can't let that go. The resistance stays the same (near enough - ok it does go up a bit with temperature but only 3% for a 10K temp rise which isn't significant), the issue is that the heat this resistance generates can't escape and this causes over heating.

Mr P - I think the plastic stuff does sound much better, and we'll use that.

It is apart for one thing... Pull a bit off a roll whilst nobody is looking and then take it outside, find a smoker and ask them to put a match to it. I believe that some now has the additives to make it fire resistant (not proof) but not all. The stuff I looked at had no claims for fire rating which made me very suspicious.

 

[Penners]

Pull a bit off a roll whilst nobody is looking and then take it outside, find a smoker and ask them to put a match to it. I believe that some now has the additives to make it fire resistant (not proof) but not all. The stuff I looked at had no claims for fire rating which made me very suspicious.

Have a read of this thread: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=772

The exchange of views between Tony Reed (who is obviously involved with the manufacture of the stuff) and a certain Mr Biff Vernon clarifies the fire resistance of this type of insulation. Personally, I have no worries about it.

 

[Lime]

Pull a bit off a roll whilst nobody is looking and then take it outside, find a smoker and ask them to put a match to it. I believe that some now has the additives to make it fire resistant (not proof) but not all. The stuff I looked at had no claims for fire rating which made me very suspicious.

Have a read of this thread: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=772

The exchange of views between Tony Reed (who is obviously involved with the manufacture of the stuff) and a certain Mr Biff Vernon clarifies the fire resistance of this type of insulation. Personally, I have no worries about it.

The pertinent point concerning insulation made from plastic is not it's flamability but the fumes and dense smoke it gives off when heated.
The fumes are highly toxic.

 

[Flyfisher]

Interesting comments about insulating the cold water tank. I'm not sure we've ever had a house with an insulated tank. I entirely agree with points about not insulating the ceiling directly below the tank and I've always assumed this was enough to prevent the tank from freezing.

Water has a very high specific-heat-coefficient-something-or-other. I forget the specifics but my understanding is that this means it can absorb a fair bit of heat and give out a fair bit of heat with a quite small change in its own temperature (hence the seas around the UK having a moderating effect on our weather). A large mass of water such as a cold water tank in the attic would require an awful lot of sustained cooling, something that is presumably very rare in the UK as I've never had any frozen tank problems despite well-insulated attics and non-insulated tanks. Pipes are, of course, a completely different matter as they contain relatively little water and can thus lose heat much faster than a large body of water, so pipe insulation is definitely a good idea.

Perhaps I've just been lucky with cold water tanks - I'd be interested in comments about this.

Joce, I can understand Chris's reluctance to insulate the attic after other draughtproofing, though I wonder if this is an excuse for putting it off. This is by no means a criticism because it is indeed an uncomfortable job, but I suspect you'll be losing more heating money through uninsulated ceilings than through draughty doors and windows.

 

[Penners]

Water has a very high specific-heat-coefficient-something-or-other.

Don't you start trying to blind me with science! :wink:

While I'm sure your that argument is mostly correct for the large mass of water stored in the tank, FF, I suggest that the ballcock valve within the tank is a vulnerable point. This will inevitably have a small amount of water inside it, which would be very likely to freeze if the tank were not insulated.

I would also have some concerns about the integrity of the tank if, as would be likely in severe winter weather, ice were to form on the surface. Its expansion could potentially cause damage to the tank, couldn't it?

 

[Flyfisher]

:lol: I think I tripped myself up with that one!

Yes, I agree that the ball valve would probably be a weak point in an uninsulated tank. I'm less sure about the risk of damaging the tank, even if it froze completely, because the open design would, I think, prevent enough pressure building up to damage the tank. But that's only a guess. If conditions became so bad that a large tank of water could freeze solid then I'm sure there would be many other things to also worry about.

I wonder how they cope in really cold countries? No tanks in the attic I suppose!

Perhaps I've just been lucky with the uninsulated tanks in our various houses.

 

[MdB]

4 degrees is the critical temperature for the body of the water. Once it cools to this point, convection stops and the surface rapidly freezes (which will cause problems for the ball cock). If it got to this point, I wouldn't be worried about the tank, it would be the pipes leading to it which would burst first I would have thought.

In a few modern properties I've seen the insulation go over the top of the water tank. Sounds like a sensible idea if it can be done easily.