Loft insulation options

[MrFoolish]

I'm thinking of getting my loft insulation improved. At the moment, it is just between the rafters. I understand you get benefit from another layer perpendicular across the top.

About a third of the loft is boarded (around the loft hatch). I never go in the loft (not comfortable clambering in and out) but have stuck my head in from the top of the loft ladder and have stuck a couple of items of junk in there. It will probably never get much use.

I think the options might be:

1. Insulate everything, including on top of the boards. Downside - lose the bit of storage space.

2. Leave some of the boards with no insulation of top. Keeps some storage space but compromises the heat insulation.

3. Insulate everything (including on top of the boards) and put in some extra boards on top of the second layer. More expensive.

I would get someone in to do the job. No idea what it would cost.

Do these options make sense? I appreciate I'll have to make my own choice but I'm interested to take views. Thanks.

[MyNameIsUrl]

I would guess if you really need some storage space it might be easier to lift the existing boards and refit on top of the new insulation. Easier than manhandling new boards through the house and up the hatch. You know about stilts I presume?

[GrahamPlatt]

or board it out with polyurethane insulating boards.

[Howard]

I'm thinking of getting my loft insulation improved. At the moment, it is just between the rafters. I understand you get benefit from another layer perpendicular across the top.

About a third of the loft is boarded (around the loft hatch). I never go in the loft (not comfortable clambering in and out) but have stuck my head in from the top of the loft ladder and have stuck a couple of items of junk in there. It will probably never get much use.

I think the options might be:

1. Insulate everything, including on top of the boards. Downside - lose the bit of storage space.

2. Leave some of the boards with no insulation of top. Keeps some storage space but compromises the heat insulation.

3. Insulate everything (including on top of the boards) and put in some extra boards on top of the second layer. More expensive.

I would get someone in to do the job. No idea what it would cost.

Do these options make sense? I appreciate I'll have to make my own choice but I'm interested to take views. Thanks.

My large loft was fully boarded. Fifteen years ago I put a thick layer of insulation over the flooring leaving just enough clear for our Christmas decorations. So it was close to your option 2. We have a loft ladder but I think the discipline of no clutter in the loft is a good one.

I'm guessing that the thick extra layer of insulation has saved well over a thousand pounds in energy costs and this year the savings are mounting up fast. The bedroom temperatures don't fluctuate so much which is a bonus.

Only problem - today I put the empty decoration boxes back in the loft and it was literally freezing up there!

regards

Howard

[MrFoolish]

I would guess if you really need some storage space it might be easier to lift the existing boards and refit on top of the new insulation. Easier than manhandling new boards through the house and up the hatch. You know about stilts I presume?

That sounds like a good option. Presumably not a big job for people who specialise in loft insulation work? I'd certainly ask them about this.

[BullDog]

I have broadly the same thing. About 125 to 150mm existing rockwool between rafters. 2/3 of loft boarded out. There's stilts made that you can fit to lift the existing boarding out and accommodate an extra layer of rockwool. I wouldn't propose adding extra layer of wool over the existing boarding out and other layer of boarding on top due to significant weight being added. Whether that's really an issue is not a question I want to answer. I'm just not considering it.

I need about 100 to 110 square metres of top up rockwool to put a further thickness of insulation down. To give me about 280 to 300mm total thickness. Less thickness adjacent to the roof eaves so as to not limit roof space ventilation.

The quotes I have to remove the existing boarding out, lay new top up insulation, fit stilts, refit the existing boarding out. Around £1500 total. That's basically £500 for the rolls of top up insulation and a £1000 for labour plus odds and ends.

I calculated that I'd save about £45 a year after spending the £1500. With today's gas tariff probably double that and a bit more to say £100 a year. Conclusion? Not economically viable.

[MrFoolish]

Thanks for all the comments, which are food for thought.

So BullDog, do you think you'll put down an extra layer of insulation, perhaps not covering the entire area?

[BullDog]

Thanks for all the comments, which are food for thought.

So BullDog, do you think you'll put down an extra layer of insulation, perhaps not covering the entire area?

Still mulling over exactly what to do to be honest. Spending £1500 is out of the question. So, it's probably in the realm of "what can I do myself for as little cost and effort to give the best outcome". I have really picked all the low hanging fruit here. The law of diminishing returns is definitely setting in.

[MrFoolish]

This reminds me that my drop-down loft hatch is uninsulated. Wondering if I could shut it up with a couple of old pillows on the top surface as a temporary measure?

[AF62]

I'm thinking of getting my loft insulation improved. At the moment, it is just between the rafters. I understand you get benefit from another layer perpendicular across the top.

You do, but it is diminishing returns so payback time may not be quick.

I added roll insulation to cover the outer 2/3rds of the area on top of that between the rafters, and then insulation board in the central 1/3 with loft boards on top.

But that was 10 years ago when insulation was cheap as it was being subsidised by the energy companies under a government scheme, and as I was doing it myself, then it cost about £100 or so, and so the payback period has been covered easily over the last 10 years.

However now at £500 for the insulation material that would be a harder decision, but if it cost another £1,000 for someone to do it (although why it should cost someone £1,000 for a single worker for one day’s work…) then that would be a hard ‘no’.

[Howard]

I'd be very surprised at today's energy costs if you couldn't get a pretty quick payback on boosting your insulation. It sounds as though it wouldn't be too difficult to roll out, say 10 rolls from your boarded area and at £25 a roll or thereabouts it might be a good investment. Doing this myself years ago it took me around two hours. If labour costs weren't too high, payback could be around two years if you are using gas at around 30p per kWh. Next year energy might be more expensive as the government won't be subsidising it as much.

Googling "grants for loft insulation" gave me links to several local firms claiming that they had access to local authority grants in my area. So it might be worth trying this and getting a quote.

regards

Howard

[88V8]

I'm thinking of getting my loft insulation improved. At the moment, it is just between the rafters. I understand you get benefit from another layer perpendicular across the top.
I would get someone in to do the job. No idea what it would cost.

I did my own top-up, but I'm only 71, perhaps in ten years not so keen....

Had about 2" up there.
Part boarded, I lifted the boards and put more wood beneath to raise some of them but decided not to refit others. Unscrewing the boards and shuffling the stuff up there around while I did so was a bit of a faff.
I kept a boarded path to the cold tank in case I need to replace the ball valve.
Laid another 6-8" of insulation. As Bulldog said, careful not to block the eaves ventilation.

I forget the cost even though it was just a few months ago, so it wasn't significant - few hundred.

Important... if your cold tank is up there you need to make jolly sure that it's well lagged, and perhaps increase the pipe lagging, as it will be colder.
As usual, do not insulate beneath the tank.

V8

[BullDog]

Varies by local authority. Here, unless you are on certain means tested benefits, have a low income and a house with very poor energy rating, it's not possible to get any council grant for insulation.

[Mike88]

This reminds me that my drop-down loft hatch is uninsulated. Wondering if I could shut it up with a couple of old pillows on the top surface as a temporary measure?

Just glue loft insulation to the hatch; that is what my contractor did.

[DrFfybes]

Firstly, increasing the old 100mm between the rafters does make a huge difference to heat retention. Just make sure they don't insulate under any water tanks!. Onve you've added 170mm top up I believe you are into the realm of diminishing returns.

Actual savings are hard to quantify, but you notice it in how quickly the bedroom cools after the heating goes off.

3. Insulate everything (including on top of the boards) and put in some extra boards on top of the second layer. More expensive.

Option 4. Remove the boards, fit loft legs (aka stilts) - £17.50 a pack of 1 from Wickes, 175mm high so reach above a 170mm roll. You used to get 210mm high ones in Screwfix to go over 200mm top up, but they seem to have stopped them. However it might be a LOT eastier to fit the loft legs to the exsiting boarding, it would just mean a step in the boards if they were later extended. Then insulate across the boards with 170mm top up insulation,

Note that electric cables should be lifted on top of the new insulation if possible, especially if you have a high current cable for a shower in there.

or board it out with polyurethane insulating boards.

A lot neater and less messy, preserves the ventilation around the eaves, but can trap moisture under them. They are the choice for insulating the slopes, but not for putting on top of the ceiling joists. Also they are about twice the price of Rockwool, and a lot harder to get through the loft hatch

I wouldn't propose adding extra layer of wool over the existing boarding out and other layer of boarding on top due to significant weight being added.

Shouldn't be a problem - the boards are relatively light (about 6kg/sqm) and the load spread over a wide span of joists. Certainly a lot lighter than the person installing them or the boxes of books you put on top afterwards. Or the cold water storage tank.

I need about 100 to 110 square metres of top up rockwool ...
The quotes I have to remove the existing boarding out, lay new top up insulation, fit stilts, refit th existing boarding out. Around £1500 total. That's basically £500 for the rolls of top up insulation and a £1000 for labour plus odds and ends.

Your figures are pretty much correct, £4/sqm for the insulation, a couple of packs of legs, and depending on working height and access, once the stuff is up there is could be 2 days' work for one person, however a lot of places simply charge per square metre.

In the bits of our roof I could get in, it took me most of a day to do 6m x 3m. However the highest point in the middle was only 30 inches and there was a timber at 18 inches from the joists half way along, the hatch was too small to get a roll through, so there was an awful lot of shuffling along crawl boards to get the roll to the far end, then unroll it back towards the hatch, then back along to push it to the side, and repeat and repeat.

Paul

[MyNameIsUrl]

...I understand you get benefit from another layer perpendicular across the top...

...I did my own top-up...

I got a small amount to do a specific area of the loft perpendicular to the existing insulation - it was supposedly pre-scored to make it easy to lay between the joists, but I found it all fell apart into narrow strips. What I expected to be a nice neat job of 1200mm wide insulation at right-angles to the existing turned into a bit of a dog's breakfast of strips that didn't really butt up very successfully. Did you have this problem?

[BullDog]

FWIW, the 22mm chipboard I used years ago when I boarded out the loft is around 23kg per sheet, around 16kg per square metre. Another layer on top - 32kg per square metre, that's why I'm not even thinking about it. Worse, the bulk of the weight is in the central 1/3 width of the roof, the joists of which are only structurally supported at the ends.

[NotSure]

I started off trying stilts to accommodate the extra insulation depth but found it a very tedious and time consuming job and not that cheap.

Ended up using this: https://www.amazon.co.uk/LoftZone-8x8USAVE-StoreFloor-Loft-Decking/dp/B00SX0VNT6/ref=asc_df_B00SX0VNT6/

Took a leisurely day or two to fit and gave me a large rectangular floored area under the centre where there was some height. I didn't bother going right into the eaves.

Very happy with it. I'd think twice about storing very heavy items (e.g. fridges) but fine for general storage and stable and secure to walk on.

[88V8]

...I understand you get benefit from another layer perpendicular across the top...

...I did my own top-up...

I got a small amount to do a specific area of the loft perpendicular to the existing insulation - it was supposedly pre-scored to make it easy to lay between the joists, but I found it all fell apart into narrow strips. What I expected to be a nice neat job of 1200mm wide insulation at right-angles to the existing turned into a bit of a dog's breakfast of strips that didn't really butt up very successfully. Did you have this problem?

Yes. Not sure what benefit is supposed to accrue from slicing it, but it didn't for me

V8

[9873210]

Stopping air leaks may be more important than extra insulation. The more insulation you add the harder it is to seal leaks, so this should always be considered before adding insulation. A few kg of caulk, foam, and filler strips are cheap but labour intensive. A good DIY job for people with more time than money.

Check the hatch. This should be installed to the standards of any exterior door or window. Is it weather stripped? Does it have a latch that compresses the weather stripping? Check the outside of the frame. It should be sealed to the ceiling, not have several mm gaps all round. One method to deal with hatches is to use foam board, weather stripping and bungee cords to form a well sealed hatch on top, so the visible hatch is purely cosmetic.