What is the best way to improve loft insulation

pinnks

Here's a non-PV question for once.

My house is 1980s with what used to be about 100mm of loft insulation which to be honest is showing its age a little and almost certainly not as efficient as it could be. EPC noted the lack of the yellow stuff.

Trouble is, my attic is boarded out, so just laying a load more insulation is not easy. One could buy those stilts but that would cost a fortune, literally, and I am not sure how stable whey would be for a walkable loft space.

One could lay new 200mm timbers (my loft is about 3m internally at the ridge) at right angles, then replace/cover the old wadding and lay 200mm thick insulation at right angles before putting the boards back down but that would add a huge amount of weight to the structure.

One could use those metal-braced floor joists which would be lighter but probably more expensive. Then there is solid insulation but that is not cheap either.

Does anyone have any other thoughts or experience, maybe spray-filled to only 100mm? No idea of the cost of that...

All thoughts appreciated.

Gary

zeupater

Hi

I simply audited what was up there and whether it could .... a) be burned/go in the bin .. or .. b) be moved elsewhere. Most of the junk up there was empty cardboard boxes for TVs, HiFis, PCs laptops, kettles, Betamax VCRs etc so it became a simple decision to lay additional roll insulation over both the boarded and unboarded areas (2x200mm over the original 100mm, each layer at 90degrees to the previous to maximise efficiency). Where easy access/storage is still required I've used 'Knauf Spaceboard' on top of the old boarding and in areas where a low profile insulation is required (such as where the loft ladder needs to lay flat and on the drop down loft hatch) the low emissivity foil roll insulation (silver bubblewrap type) is useful ... we also have a walk-through door to another loft and one to the integral garage which have been backed with the foil insulation ....

With all of the insulation in the main loft, in addition to the existing water header tank jackets, I've made additional insulation by enclosing spare 200mm insulation in plastic and then wrapping this around the tanks and tying into place .... nearly forgot - don't forget to have a look whether the holes punched between the house and loft for water pipes are sealed to prevent air/heat leakage ...

Food for thought ...
HTH
Z

pinnks

Z

Thanks. Done the ceiling holes and the clear-outs. Indeed just doing one of those which is what got me thinking about this again.

I would say I'll be using about 33% of floored area for storage but I do like the freedom to put that wherever I want and to walk securely and safely up there. I suppose I could get a bit more disciplined about where I store/walk and cover the rest of the flooring.

Bit of a rock and a hard place issue...

nobby1963

Hi pinnks,

Hope you don't mind me jumping into your thread a bit .....I've been pondering this issue myself for what seems like years now.

One thing I was told was to be aware of the weight of any additional materials you end up putting in the loft to achieve the goal of deeper insulation. By that I mean if you went down the road of putting more timber up there to increase the depth of insulation you could fit between it then there could be structural issues if there is too much timber and therefore weight - does that make sense ?

I've been curious as to whether there is nowadays more efficient insulation that I could use between my loft timbers that are only able to fit a more shallow amount of insulation between them than is now recommended.
My house was built in the early 1980's and I would like to have a boarded / partially boarded loft for some storage but as the timbers don't have a deep enough recess between them I have an extra layer of insulation lying at right angles to the timber on top so can't board on top of that without the stilts / extra timber you talk about.

Anyone any thoughts ?

Nobby.

Alter_ego

You could consider insulating at rafter level, but don't forget ventilation.

Martyn1981

Hiya pinnks, do you have easy access under the boarding? You could replace the 'fluffy' with PIR insulation (like Kingspan), it's not cheap, but roughly twice the efficiency, and you can shop around for damaged stock.

That stuff is also very, very strong, so you could cover the floor with a layer, say 50 to 100mm, then top it off with some cheap 6mm ply, just to stop things digging into it, or getting yourself stuck if you like to wear high heels!

[Sorry, Z beat me to it. M.]

Mart.

pinnks

Thanks all. I agree weight needs to be kept in check for the reasons stated and had also thought about the kingspan type foam boards, though not seeking damaged stock - good tip.

The boards were put down by me and screwed so can come up again to do whatever I do. Subject to cost, an answer could be 2 layers of foam boards with protection on top. Thinking about it, if they are stable enough to take a person or similar load, one could presumably protect them with 6mm ply or even hardboard, rather that 19mm chipboard or ply?

After penning the original post, I did a bit of searching on the interweb and found what might be a sensible option. It's called Loftzone and is a cross between those plastic stilts and additional joists. I.e. plastic supports with metal joists on top. Not cheap but also not that much more expensive than stilts, which seem to run at about £10 per sq. meter.

I also wondered about I-beams, which are much lighter than ordinary timber but overall the foam board and hardboard protect might be the way to go.

Thoughts anyone?

ed110220

What I did was to fill between the joists with 100mm roll insulation then put down Knauf Spaceboards (precut 1200 x 450mm insulation boards designed to fit through the average loft hatch) on top, then finish with a deck of the usual tongue and groove chipboard.

The Spaceboard was not cheap for what it is though, but having a proper floor up there was a requirement for having a boiler fitted in the loft. It would be cheaper but more fiddly to buy some of the larger insulation boards and cut them into smaller pieces yourself.

Knauf says if your loft is already boarded you can put the Spaceboard on top of the existing boards and then lay new chipboard on top, but I'd prefer to take them up and do it from the non-boarded state.

ed110220

Took the photo to show the pipework I put in for the new boiler so the fleece type insulation is a bit displaced, but you can see the deck build-up.

Ed

pinnks

Ed,

That looks interesting. So, based on comments above, I guess you have a broad equivalent of about 300mm of the fluffy stuff. Leaving cost to one side, I guess there is no reason why one couldn't go 200mm of boards and 100mm of the fluffy stuff if headroom is not an issue.

What slightly concerns me is the (not quite) point loads on the foam boards where they sit on the joists. Presumably, that is not an issue because if you start approaching that limit you would have so much point weight on that particular board that you risk collapsing the whole roof structure?

If I do the whole roof space, I need to budget for nearly 50 sq. meters, plus new fluffy stuff as mine is looking well tired. Not sure what period I would need to recoup the investment but at the very least the house should be warmer...

zeupater

pinnks wrote: »

... What slightly concerns me is the (not quite) point loads on the foam boards where they sit on the joists. Presumably, that is not an issue because if you start approaching that limit you would have so much point weight on that particular board that you risk collapsing the whole roof structure?

If I do the whole roof space, I need to budget for nearly 50 sq. meters, plus new fluffy stuff as mine is looking well tired. Not sure what period I would need to recoup the investment but at the very least the house should be warmer...

Hi

The Knauf Spaceboard is pretty expensive compared to standard loft insulation, so unless you've got really deep pockets look to use it sparingly. I laid somewhere around 12-15sqm of it over a boarded area in one of our lofts which was already insulated beneath and simply placed some boards over it to form a walkway, anything which is in storage simply sits on the Spaceboard, that way there's no difference to the loading.

HTH
Z