Insulation advice

allybhoy

Long post, apologies in advance...

Last summer we bought a 4 bed detached house...we had a company in to replace the gas boiler as it was broken, we asked them at the time whether we should look at also increasing the insulation (same company also did both) and they advised us to live in the house for a few months to see whether we thought it was required as the new boiler was far more efficient at heating the house. last winter we found the house extremely cold in t if the heating was off and so we pretty much had it on constantly during the cold months and ran up a large gas bill.

So, im going to look at upgrading the insulation myself... There is insulation in the attic but its very patchy in places and and definitely not of the required thickness as its probably in situe since the house was built over 15 years ago. I bought 6 rolls of Earthwool Loft Roll 200mm and plan on topping up every part of the existing insulation and plugging any gaps i find and i also bought several rolls of YBS Airtec Reflective Insulation.

However ive had several people advise me differently on how to best install this. Some are saying that i should staple this to the rafters in the roof and others are saying that i should simply lay this on top of the earthwool and staple it to the ground.

There is no insulation at all between the rafters, so my theory to laying it on the ground was that u are ensuring that heat stays trapped between the attic floor and the house, however i have read in some places that this wont work as the reflective insulation needs an air barrier between it and the Earthwool.

Lumen

"reflective insulation" = snake oil.

Most losses are conductive (for which you insulate) and convective (for which you ensure air tightness).

The two approaches you're alluding to are cold attic (insulate joists) vs warm attic (insulate rafters). Both are valid approaches. The easiest to get right is cold attic, which is why it's the most common.

The simplest approach is to put one layer of insulation between the joists and another over the joists at right angles. And put down boards where you need access e.g. to tanks.

This doesn't solve the air tightness issue - you can get warm air pulled through the insulation by wind-driven pressure differences.

BryanF

Make sure Eaves ventilation is maintained

allybhoy

Lumen wrote: »

"reflective insulation" = snake oil.

Most losses are conductive (for which you insulate) and convective (for which you ensure air tightness).

The two approaches you're alluding to are cold attic (insulate joists) vs warm attic (insulate rafters). Both are valid approaches. The easiest to get right is cold attic, which is why it's the most common.

The simplest approach is to put one layer of insulation between the joists and another over the joists at right angles. And put down boards where you need access e.g. to tanks.

This doesn't solve the air tightness issue - you can get warm air pulled through the insulation by wind-driven pressure differences.

Thanks for this, I already have sufficient boards down for access to tanks and storage etc
So to sum up, i should top up the insulation, plug any gaps and then lay additional rolls of sheepswool insulation in the opposite direction across the joists . Is there any benefit at all to then laying the reflective bubble insulation on top of the above again? I have 50 square metres of it so id like to use it somehow..

Lumen

allybhoy wrote: »

Is there any benefit at all to then laying the reflective bubble insulation on top of the above again? I have 50 square metres of it so id like to use it somehow..

Sure. The "snake oil" comment was w.r.t. the difference made by the reflective element.

allybhoy

Lumen wrote: »

Sure. The "snake oil" comment was w.r.t. the difference made by the reflective element.

Cheers, is there any concern i need to have in regards to condensation etc about laying it flat?

Lumen

allybhoy wrote: »

Cheers, is there any concern i need to have in regards to condensation etc about laying it flat?

On top of the other insulation? Yes. Don't put a vapour impermeable layer on the cold side of the insulation, it should go on the bottom (warm side). If you were doing the rafters instead it might make sense to put it on the warm side (bottom) of those.