insulating loft over boards

morg_monster

Hi, we are moving into our first house on friday (woo!)

Seeing the £1 a roll offer on rockwool insulation has got me thinking about the loft. According to the HIP the loft only has 5cm of insulation and was unboarded, so we had plans to improve that ASAP. But when we went to measure up a month ago the vendor told us that her husband had spent the weekend in the loft boarding it over. Doh! It looks really good, but obviously makes improving the insulation a bit more difficult.

At the moment we probably won't really need the loft for storing stuff(moving from a 1bed flat to 3bed house) but I don't think it'll be long before we start to accumulate things! So I am kind of wanting to keep the loft boards if possible.

So my question is, is it possible/any good to just lay down insulation on top of existing boards? Will it have any effect on the heating bills? I have researched but have seen differing opinions on this, my physics A-level says it will help but not as much as installing it "properly"!!

Also, if it is OK, would it complete ruin the whole point if we leave a small part uninsulated to store a few boxes in?!

If this isn't going to work, I'm not sure what to do. Taking up the boards and adding insulation will mean we can't use the loft for storage unless we raise the joists, which I don't really fancy and we can't afford at the mo ... As far as I know the house is not particularly difficult to heat (we visited during a cold period) but obviously the bills could be astronomical for all we know.
Any ideas?! Ta.

casper_g

I wouldn't have thought having a layer of boarding in the middle of the insulation would make much difference -- 50mm insulation + loft board + 100mm insulation can't be worse than 150mm insulation on its own, surely?

If you need part of the loft for storage you can always use rigid insulation in that area. You can get boards made of rigid polystyrene that are strong enough to store things on. They're more expensive than normal insulation but might be an easy way of doing what you want.

lagi

A simple solution would be to use a wooden pallet. this has openings underneath that if layed correctly would allow your second layer to still criss cross over the top. A good base to store things on. Obviously sit on the joists well. Maybe even screw it down.

As for moving from a flat to a house, you will soon need storage. We are a nation of hoarders.

WestonDave

You can get something called SpaceBoard - which is a rigid type of insulation that is designed for areas needed for storage. Technically you can just put it down on the joists and then walk on it - I wasn't that confident so added some spread out boards first to help bridge the gaps, then put down two layers of SpaceBoard (which with 100mm down between the joists is the equivalent of the full recommended amount), and then put proper boards on the top for walking/storage. However I only did a central strip for storage and did traditional insulation in the remaining areas. Last year Focus were selling SpaceBoard on BOGOF, so its worth watching out for deals like that. Its not cheap, but once done is a long term solution, and its seriously a lot less hassle than raising the joists!

andrew-b

lagi wrote: »

A simple solution would be to use a wooden pallet

You sure...how big is your loft hatch?!
Really don't see there would be a problem with laying the insulation on top of the boards. However if the existing insulation under the boards has squished down it would probably be an idea to squash some 100mm under the boards to fill the air gap (leave the old stuff there - too much hassle removing/disposing) . 100mm squished to 50mm plus existing 50mm has to be better than 50mm.

Though do note that loft insulation relies on air within it so squashed insulation is less effective than unsquashed.

To raise the floor 170mm above the ceiling joists to accomodate insulation is a bit of an awkward dimension to deal with as it's not a dimension timber is commonly available in. Got to try find a way to raise an area myself - a walkway to water tanks and a smallish storage area - though i suspect i may give up in the end and leave an area without insulation above the ceiling joists!

lagi

andrew-b wrote: »

You sure...how big is your loft hatch?!

Forgot about that, its because i have no ceiling up at the moment upstairs. Scrap that idea. Unless you dismantle it and put it back together again.

morg_monster

Thanks guys looks like it is going to work out after all! Now best get on and see if i can get some of that £1 a roll insulation!