I want to redo our loft insulation but not sure if it's too big a DIY job!

ashe

We had a quote for loft insulation and it came back as £588 inc vat but that was about a year ago so assume about £30k with current prices 😂

jokes aside, that was for 55 sqm of "Loft insulation 200mm thickness using Knauff Earthwool"

But Having gone up in the loft to assess it as part of doing some other jobs, I'm not convinced on just having them lay it. 

Currently our loft has what looks like 100mm of old yellow insulation which is probably original to the house as it has a thick layer of dust / dirt in it. 

Over time this has been moved out of the way for various pipes to be installed, our boiler is situated in the loft and there have been down lights and extractor fans installed in the loft. 

When the company came out to give us a quote for the insulation they said it would be fine to just roll it out over the spotlights as they're low energy led and don't get hot like the old ones. Yet websites seem to suggest that we need fire hoods on these (there are 20 total) and presume there will be some transformers there too (haven't looked - is there one transformer per light or one for all lights on the circuit?)

If it's a straightforward job I am happy
enough buying the insulation in and laying it, but have a few questions 

1) is the suggested insulation above the best variety to use?or any other recommendations? 

2) will I be ok to lay it over this existing old insulation or am I best of stripping that out and getting rid and doing a layer of 100mm and then trying to cross-lay in the other direction with the 200mm stuff?

3) there are some wires that run along the joists - I presume these are all just lighting cables, extractor fan cables etc as we don't have an electric shower, but a bit worried about these going under insulation, some websites say it's fine, some say it's a huge no ? 

4) where we do have cables running, or pipes running through the loft, I presume it's wise to make where these run? Is there any product for this eg a spray marker to mark where condensate pipe, water pipe, cables are routed etc? Similarly with joists so it's obvious where it's safe to walk on?

5) some websites suggested a clay plant pot over the down lights would be effective and far cheaper, but not sure if will have same effect?

6) there are a few cables in the loft from probably previous works up there where there are some bare electrical cables without terminator blocks on them or anything. I presume these aren't live as they are just sat on the existing insulation and would assume that would be a fire risk already? We've got some electricians in doing some work tomorrow so am going to ask them if they can confirm those aren't live - if I come across any more when doing the insulation, is there any safe way I can confirm this myself?

7) I think it's advised to not insulate right up to the rafters, and I'll install some lap vents while I am at it; our loft hatch is basically a piece of plywood, is there anything I need to do to insulate around that as presume that would be a big source of heat loss 

Below is a pic of the current loft insulation that is in situ - house was built in 1999 and presume it's from then 



 

grumbler

1) IMO, difference between different types of mineral wool insulation is small. The suggested one is good and, IMO, better than glass wool types.

2) Yes, their is no point in replacing the existing one.

3) It's better to have wires on the top, but not necessary. And it can be a big job to redo all of them.

4) I dont' know. Spray paint will work. However, walking will become very tricky when you add extra 15-20mm of insulation. Consider boarding the loft, at least partly, over the insulation.

5) Clay pots are fine IMO if you can't find anything cheaper. If you have low-voltage lights and transformers, I would take all transformers out and fix them to rafters.

6) Don't presume anything. Remove cables or terminate them. To check them you need a decent multimeter. If you don't know how and can't trace the wire, leave it to a professional.

7) Yes, don't block the eaves - this requires some compromise between insulation and ventilation.

ashe

Deleted_User said:

That looks very much like my loft! Built a few years later. We have lots of down lights in the extension and the builders have just left the insulation with a little gap - so that's definitely something we need to address - and the firehoods are expensive.

Watching with interest. I'm not convinced I need more (house is warm enough) but it's something I'm still mulling over. 

I think I need more as the edges of insulation around the joists will will allow hear to escape there so by laying it in the other direction there should be some protection from that 

ashe

grumbler said:

1) IMO, difference between different types of mineral wool insulation is small. The suggested one is good and, IMO, better than glass wool types.

2) Yes, their is no point in replacing the existing one.

3) It's better to have wires on the top, but not necessary. And it can be a big job to redo all of them.

4) I dont' know. Spray paint will work. However, walking will become very tricky when you add extra 15-20mm of insulation. Consider boarding the loft, at least partly, over the insulation.

5) Clay pots are fine IMO if you can't find anything cheaper. If you have low-voltage lights and transformers, I would take all transformers out and fix them to rafters.

6) Don't presume anything. Remove cables or terminate them. To check them you need a decent multimeter. If you don't know how and can't trace the wire, leave it to a professional.

7) Yes, don't block the eaves - this requires some compromise between insulation and ventilation.

Thanks for the info. For the loft hatch can you just put some insulation board in the back of it the same size as the hatch to prevent that leaking heat? 

grumbler

 Yes, a piece of 25 mm of celotex would be fine, but IMO sealing all gaps to stop air flow is even more important.

ashe

grumbler said:

 Yes, a piece of 25 mm of celotex would be fine, but IMO sealing all gaps to stop air flow is even more important.

I take it you mean around the loft hatch? I reckon probably some from down lights as well as they won't be air right but presume some coverings on those will help with that. 

The batch is a fairly tight fit and don't think I'd get anything else around that, but could put some adhesive foam around the hatch to prevent anything going up the edges 

grumbler

ashe said:

grumbler said:

 Yes, a piece of 25 mm of celotex would be fine, but IMO sealing all gaps to stop air flow is even more important.

I take it you mean around the loft hatch? I reckon probably some from down lights as well as they won't be air right but presume some coverings on those will help with that. 

Yes, around, like for any window or external door.

For the lights, don't rely on covering. Usually they have some sort of thin foam washer. If not, you can improvise something similar.

MisterNick

https://forums.moneysavingexpert.com/discussion/comment/79526578#Comment_79526578

I posted this back in September (5th post down) I have pretty much finished now, although I still have to move the "stuff" back into place.

We had that yellow insulation previously and it was horrible to remove coupled with rat and mice skeletons and droppings. I bought a full suit and used marigolds mask etc. The new insulation was a lot less bother although I did use a mask and gloves. 

I used the lid covers for the lights in the bathroom, but all others I left as is. We had a lot of wiring done when we moved in and the electrician (who we still use) would have told us to sort it earlier  

Similarly, I left any wires attached to the joists where they were in place, and any over the insulation previously I placed on top of the new insulation. These were mainly aerials and satellite.

If you don't currently have boards to lift and replace on loft legs, it will make the job a lot easier. Grumbler is correct in that you will not be able to move around on the joists, and should put in some raised boards. The loftlegs were good for me. Pre screw the bottom ones first as it will make life easier. I can't comment on the adding upturned planks to support the boards.

I am no expert so can't comment on whether you should go over the old insulation, but in my case I was pleased I did, especially as a lot of it had rucked up and was quite awful.

You are correct about not insulating up to the rafters. With the 100mm insulation down first you can get quite close whilst still leaving a gap and the thicker insulation on to comes a bot short. A bit difficult to explain, but it is intuitive.

I did leave the area as you step off the ladder and into the loft at 100mm to create a sort of landing area which makes it easier for moving stuff out and putting it back (Christmas dec boxes and so on.
I still have to do my loft hatch. i was going to use celotex but i have a drop down hatch and a pull down ladder. When it is down there is not quite enough space between the top of the ladder and the hatch hanging behind it.

Like I said I am not an expert, so can't give technical advise but hopefully this from a non DIYer is helpful. 
I did buy one of these;
https://www.screwfix.com/p/magnusson-retractable-25mm-snap-off-knife/7062v
 to cut the insulation and it was very good, particularly with the thicker one. Look online for how to cut it as doing it the right way is much easer 
Don't underestimate how restrictive it is in there, and how you have to balance support boards to get around.

I went out this morning and the roof was completely white, which it wouldn't have been before, That made it all worthwhile

fenwick458

grumbler said:

5) ....... If you have low-voltage lights and transformers, I would take all transformers out and fix them to rafters.

I wouldn't do this, it would mean that whenever the transformers fail you have to go up into the loft and start digging around in the insulation, probably doubles the cost of replacing and the time taken rather than just pulling it out the hole from below

a better solution would be to just fit 240V LED replacements, get rid of the transformers completely

grumbler

MisterNick said:

 

Similarly, I left any wires attached to the rafters where they were in place,....

...you will not be able to move around on the rafters,

joists - to avoid any confusion.

MisterNick

grumbler said:

MisterNick said:

 

Similarly, I left any wires attached to the rafters where they were in place,....

...you will not be able to move around on the rafters,

joists - to avoid any confusion.

Thanks - I have corrected.