New build Insulation

kenneth2

Just wondering what people recommend for insulating a new build ?
some people recommend just insulating the interior of the external walls,
and leave the cavity free
(they say the cavity is a waste of the ineternal ins insulated )
and others say to insulate the cavity and the interior of the external walls.

What's the feeling like here ?
and what is the best internal insulation spec (100mil insulated plaster board)?

We've started builing and i've been told that the cavity insulation is a waste if using the internal insulation aswell ?

Also i was thinking if i pumped in insulation later, it would seal up the house aswell ...?

sydthebeat

kenneth2 wrote: »

Just wondering what people recommend for insulating a new build ?
some people recommend just insulating the interior of the external walls,
and leave the cavity free
(they say the cavity is a waste of the ineternal ins insulated )
and others say to insulate the cavity and the interior of the external walls.

What's the feeling like here ?
and what is the best internal insulation spec (100mil insulated plaster board)?

We've started builing and i've been told that the cavity insulation is a waste if using the internal insulation aswell ?

Also i was thinking if i pumped in insulation later, it would seal up the house aswell ...?

To be very frank, you need to have these decisions made before you start building, for a few reasons:

1. you need to comply with building regulations. In order to do so you need to have a DEAP assessment done BEFORE you start work to ensure the materials you are putting into your house comply with regulations. If you have not done this, you run the very real risk of not complying and having to spend significant money, after completion, in order to comply.

2. you need to know what dimensions of construction you need to comply ie do you need 150 rafters, or 175 or 225?... will you be counter battening over the rafters?? or will you be insulating under the ceiling joists?? will this affect your floor to ceiling heights etc.... what depth do you need for your floor etc.... what width cavity do you need if pumping to comply....

3. your levels of insulation and air tightness directly inpact on the output demand of the boiler you require.


All your questions are relative to the whole build... you should not be dealing with insulation as a separate, isolated issue, but rather as as an integral part of the whole build where insulation, air tightness, heating controls, heating source and ventilation are all designed to complement each other.......

Radiotower

I dont think there's much point in doing both. I'd go with the insulation in the cavity. The internal block wall has a certain thermal mass which means it absorbs heat and releases it slowly. If the cavity insulation is done correctly and a good quality insulation used then the heat released from the blocks will have to go into the house and not be lost to the outside. You lose this benefit with insulated boards.

Maybe you're worried that the cavity insulation wont be done correctly but if you have a competent builder it shouldnt be a problem. I dont know much about pumped insulation but assumed it was more used for upgrading older builds. Best to ring around and get comparitive prices. The builder might knock off something of his price as he wont have to install the insulation as he builds.

How far along is your house now? The builder should be putting in the cavity insulation as he lays about every 3 courses of blocks... You'll need to order the cavity ins the same time as the blocks

kenneth2

Thanks for the comments