Should I insulate from the outside or not

[platforminc]

Hi All.

We are currently in the middle of extending our house, and I have a dilemna concerning insulation. About 4 yrs ago, we did some internal insulation to the house as the heat loss was just too bad. What we did was do use 75mm cls studs with 50mm celotex finished with plasterboard.

In hindsight, what I got to learn was that it ought to have been overboarded with insulated plasterboard, i.e 25mm insulation over standard plasterboard, its difficult to measure how efficient the internal insulation is, but we have another opportunity to put things right.

I have a picture below illustrating what we currnetly have, the bottom bit of the house which is 1m from DPC is a cavity wall which is not insulated, everytime the company compes around, they say its only 1m and not worth thier while to insulate it, this was another reason why we insulated from inside. Please advise on wht to do about the areas shaded in green.

1. Leave as is.
2. Overboard with insulated plasterboard from inside.
3. External wall insulation from outside, please note that for external wall insulation, I do not wish to cover the bottom 1m brick, I like original brick feature and want to keep this.

 

[oldbutnotdead]

Cost wise there's not a lot of difference. EWI gives more thermal mass to the heated bit (so internal temps will vary slowly) plus you don't lose room area & don't have to rewire/move rads etc.
Downside, you'll lose your brick feature, if this is a dealbreaker then consider replicating it with brick slips or vacform cladding

 

[^woody^]

Each property its different and needs to be properly assessed for EWI, or risk mould and rot all over the place.