Attic insulation board stilts?

s7ryf3925pivug

Has anyone put boards over double layers of insulation in their attic? What approach did you use and how do you find it?

The simplest approach is to just put boards on top of two layers of insulation. This obviously squashes it and makes it less effective, but apparently it is still better than using one layer.

You can get attic insulation board stilts that seem generally well-reviewed. They don't look that stable to me though. I guess they'd work well enough so long as a full platform is made that is tight enough together.

Other DIY approaches with cut timber might be cheaper and/or more stable?

Calibos

Something like 85% of the insulation efficiency is in the first 200mm another 10% in the next 100mm upto 300mm and the remaining 5% in anything over 300mm. The law of diminishing returns seems to apply to loft insulation in a big way. I'll be DIY insulating an attic after we get a new larger, air-tight and insulated Loft hatch and Ladder fitted. Just going for 150mm loft roll between the ceiling joists and the thickest Foam insulated Loftboards I can find. If thats 75mm, I'm fine with that. If its 100mm, great. No matter what though it'll be below the 'recommended' 300mm and I don't care. Like I said, 85% of the heatloss savings are in the first 200mm anyway and I'll have that. Not interested in losing storage space and messing about with stilts under the attic floor.

Thats me though.

s7ryf3925pivug

Calibos wrote: »

Something like 85% of the insulation efficiency is in the first 200mm another 10% in the next 100mm upto 300mm and the remaining 5% in anything over 300mm. The law of diminishing returns seems to apply to loft insulation in a big way. I'll be DIY insulating an attic after we get a new larger, air-tight and insulated Loft hatch and Ladder fitted. Just going for 150mm loft roll between the ceiling joists and the thickest Foam insulated Loftboards I can find. If thats 75mm, I'm fine with that. If its 100mm, great. No matter what though it'll be below the 'recommended' 300mm and I don't care. Like I said, 85% of the heatloss savings are in the first 200mm anyway and I'll have that. Not interested in losing storage space and messing about with stilts under the attic floor.

Thats me though.

Yeah that sounds good. I found another thread here since my original post and PIR attached to loftboards was mentioned. That would be far preferable to me. I'm just trying to figure out what I need to make it ok to walk/crawl/slide on. (The roof is pretty low in most of my attic.) Not comfortable with the idea of walking on the stilts and I think most people that do walk on them have used them across the whole attic, with one integrated platform on top - which would be way more stable than smaller areas.

Was trying to find details on VOC emissions of insulated loftboards. If I cant find low VOC ones I'll probably get smartply (low voc plywood product) and attach it manually to PIR. Need to know what thickness and if I need ply on top and bottom to make it safe to walk on etc. (I'm somewhere between 90 and 100kg.)

s7ryf3925pivug

I did some DIY insulation on my attic door with wedges of expanded polystyrene wrapped in tin foil. where the wood is thickest is still bare. It's in my bathroom which has the dubious benefit of illustrating where it is coldest via patterns of mould growth - and that is where it is insulated. Might stick a layer of something that can be exposed to damp on the outside too.

frankled

I am currently doing this job, I have old insulation in between the joists and a thick layer of new insulation running perpendicular on top of this from a recent (2 years ago) energy efficiency job on the house

As a result, I was torn between getting timber to run parallel to the newer insulation for the purposes of laying boards on top, or loft legs. As the newer insulation is approx. 270mm high anyway, I've gone for the loft legs which are exactly this height. To be honest I am not sure how much easier lengths of timber would be, I don't know if you would get anything that high and it would be an awkward job getting them into and around the attic to be fair.

My next choice was between chipboard tongue & groove flooring (8ft x 2ft) or the smaller loft-board packs of same (4ft by 1ft). I went with the smaller packs, again as it is just me doing the job getting the big boards into the attic just wouldn't have worked I don't think.

Anyway, I'm half-way through the job and can't complain so far. The cheapest place for the above supplies was B&Q and the boards on top of the loft legs are actually quite secure- you use 6 boards to support one board essentially.

_feedback_

Also did the loft legs job recently enough and they're really solid. Easy to work with too.

Was in Homebase yesterday and think I saw they have an offer on the legs at the moment

dathi

Calibos wrote: »

150mm loft roll between the ceiling joists and the thickest Foam insulated Loftboards I can find. If thats 75mm, I'm fine with that. If its 100mm, great. No matter what though it'll be below the 'recommended' 300mm

.

the 300mm rock wool /glass fiber is to achieve a U value of 0.16 this is calculated using the thermal conductivity of the insulation different insulation's have different thermal conductivity values and as the foam loftboards have a better thermal value than rock wool you need less, so the 150mm plus the loftboards will get you a u value of 0.16

s7ryf3925pivug

I'll probably get the solid boards. My attic is low already. The solid boards seem a bit more versatile and a bit less time consuming to put in place.