External insulation - worth it?

[Alkers86]

The effect

I've the same conundrum, was quoted 20k net of grant last year to do my (detached) house. My gas bills cost roughly 1000 per year so even if it saved me 33% as the installers usually claim, it'd take me 60 years to make that back. OK gas prices and carbon taxes will likely go up in the future but the ROI would still be extremely long. Hopefully they'll be better grants/incentives in the next few years to make this more viable.

If I needed to get the house re-plastered anyway though I think I'd probably go ahead and do it.

The cost of energy, particularly the burning of fossil fuels for home heating is likely to increase dramatically over the next 60 years.

Depending on the existing windows, I would actually wager you'd earn a payback quicker with the EWI.

 

[JohnJay]

The cost of energy, particularly the burning of fossil fuels for home heating is likely to increase dramatically over the next 60 years.

Very true. But chances are that technology and the quality/effectiveness of insulation will also improve. So the 100mm of insulation we use in 2020 might be obsolete by 2030.
Its not long ago that we thought 80mm of yellow fiberglass in our attic was the best thing since sliced pan!

 

[shweeney]

If your heating bills aren't that high, why are you even considering it?

Eliminating draughts might give you better bang for your buck.

 

[roker]

When you say internal insulation, does that mean cavity or inside the house?
There has been stories of cavity insulation causing dampness by blocking the air space in the cavity, is this a concern, has anyone experienced it?

 

[Black_Knight]

When you say internal insulation, does that mean cavity or inside the house?
There has been stories of cavity insulation causing dampness by blocking the air space in the cavity, is this a concern, has anyone experienced it?

I would consider internal insulation to be dry lining the internal walls of a house.

 

[Prosper]

There has been stories of cavity insulation causing dampness by blocking the air space in the cavity, is this a concern, has anyone experienced it?

Can you not pump insulation into the cavity?

SEAI say the absolute minimum cavity for pumped in bead insulation is 40mm and in the UK it's 50mm. My house was built in 1987 and the cavity is only 30mm when you subtract the width of the aeroboard polystyrene that's in the cavity. So in some cavity walls the pumped insulation is not appropriate.
Also, is it allowed to put up external insulation on a terraced house without the agreement of neighbours on either side? I don't know the answer to this but I would have thought you'd need the neighbours agreement.