Insulating across beams & deliberatly leaving loft poorly insulated

ScoobieGirl

I'm looking to top up my insulation, and I've read a few times that you shouldn't insulate across the beams. Would you get better insulation if one layer came up to the beams and the second layer went across the beams. Does it have anything to do with not covering the electric cables?

Any idea how a layer of tongue and groove floorboards compares? By the time it's covered in my junk, it's got to be comparable surely?

Also my friend recently removed his water tank, but hasn't insulated where it was because he claims it better for what he stores up there. It sounds like it makes sense, but a bit of a waste of energy. And thought?

Avoriaz

I can’t think of a reason not to insulate above the joists (beams) other that you don’t then know where they are and you are likely to put your foot through the ceiling below. If you don’t have flooring in your loft and want to add insulation, I suggest that you take it to about the top level of the joists.

Wooden floorboards will have very little insulating effect and nor will a pile of junk.

If you are putting flooring up there, top the insulation up so that it is level with the joists and then lay the flooring. Make a note of where all the electric cables and any water pipes are for future maintenance and don’t put a nail through them. Maybe mark the flooring to show where the pipes and cables run.

The reason why the area under a water tank is normally left uninsulated is to help prevent the tank from freezing. The rising heat helps keep the water in the tank above 0C degrees in cold weather. If the tank is removed it makes sense to then insulate that area. The small amount of heat from an uninsulated area is unlikely to make any difference to the loft as a whole as it will disperse with the slightest draught.

ScoobieGirl

Thanks for your reply.

At the moment it is up to the joists, but this is woefully short of the 10 inches that the energy saving websites recommed.

Insulating above the joist seems okay, its across them that the instruction tell you not to do. I can't think of any good reason either!

Looks as if I'll have to take the floorboards up again as the insulation under there is pretty patchy.

Lord_Gardener

It'll be worth checking to see if you can get a grant!

http://www.heatproject.co.uk/

ScoobieGirl

This site seems good too.

http://www.est.org.uk/myhome/gid/index.cfm?sec=1

Still seems a lot cheaper to do it yourself. This seems like a nice guide.

http://www.diydata.com/projects/loft_insulation/loft_insulation.htm

Can't seem to find any of the glass fibre online to compare at either B&Q, Focus or Jewson. I'll have to pop in during the week.

ictmad

i got a grant to do mine, but never heard of going over joists they just doubled mine upt+g flooring will be expensive,just double up ur loftroll and put caberfloor down if u need it floored

ictmad

ScoobieGirl wrote:

Can't seem to find any of the glass fibre online to compare at either B&Q, Focus or Jewson. I'll have to pop in during the week.

we sell rolls of loft roll either 100mm or 150 mm thick think they do about 10.6(ish) square meters very popular all the big builders ronud us use 100,s of rolls

ictmad

wickes have both and 170mm also

http://www.wickes.co.uk/icat/liloftrollinsul

Poppycat

We did our joists with Kingspan, insulated panels but we fastened it to the joists so there was always air to flow between the joists and the slate roof. You have to leave a gap for air to flow so as to reduce condensation which should build up if you didnt and rot the joists.

ictmad

Poppycat wrote:

We did our joists with Kingspan, insulated panels but we fastened it to the joists so there was always air to flow between the joists and the slate roof. You have to leave a gap for air to flow so as to reduce condensation which should build up if you didnt and rot the joists.

we sell xtratherm(same as kingspan diffrent name) but xtratherm is very expensive compared to loftroll and doesnt do as good a job

Poppycat

We only insulated it tbh because we were going to turn the loft for more storage and kids to play in. The celings are insulated and boarded up