Renovation - insulation and heating options

Feeling hopeful

Hello, we're currently renovating a 3000sqft detached house built c1970. We're doing an extensive renovation including insulation, new heating, windows doors, internal and external rendering/plastering. Have been looking at choices for internal v external insulation and heating system types. Engineer is advising external insulation with air to water and PV panels. QS, being ever so practical and economical, is advising internal insulation and gas heating. House is cavity wall so there is an option to pump cavity and then internally slab. Main concern with this is possible damp issues. Have heard of some awful examples of external insulation gone wrong plus QS argues that you’re heating the thermal mass of the cavity which isn’t the case with internal insulation. I understand that external is slower to heat but slower to cool etc than internal. Also concerned about the render on the external. The house is surrounded by a lot of mature trees and we’re worried about discolouration of the render by damp/mould etc. Also worried the specialised render might not be as robust as regular render.

With the heating the house won’t be airtight as such (new doors/windows/roof so will be as sealed as we can get it with that) so wondering if the payback for air to water would be worth it or if we should just go with gas heating (house is on gas mains) and possibly solar for hot water.

There’s obviously a cost factor as well for both heating system and insulation but don’t mind forking out up front if its worth it in the long run. Any advice at all is much appreciated.

Idbatterim

the internal insulation makes far more sense to me, particularly seeing as you are gutting the place!

are you on a natural gas line?

how much is the air to water system and pv panels?

BryanF

External insulation makes far more sense to me

Seeing as how it's continuous.

Idbatterim

it doesnt to me, the house heats up much quicker with internal insulation and holds the heat inside the envelope of the room...

Caillte

The OP QS is right, the thermal massivity of the house using ex insul will be a real saver in heating costs and as Bryan said the continuation of insulation is key to it all.

The other benefit of external insulation is that you can run new services externally on the block/brick, giving you better options to run services. In the end the ex insulation covers it all up.

sydthebeat

Idbatterim wrote: »

it doesnt to me, the house heats up much quicker with internal insulation and holds the heat inside the envelope of the room...

the advantages of external insulation over internal insulation has been debated many many times already on this forum.

Feeling hopeful

Thanks for the replies. So consensus seems to be external, thought maybe with the added cavity insulation on top of the internal slab it might have made a difference. Any concerns over the specific render used with EI? Will be a few kids running around outside plus area is wooded and am worried about discolouration/damage of the render.

With the heating the house is on a gas mains and currently has gas heating (which needs to be replaced). Like the idea of something renewable with lower running costs but not sure the air to water will give enough payback if the house isn't completely airtight. Any advice?

Metric Tensor

If you are on the gas mains in my opinion it is a no brainer to use gas central heating. The payback period for any semi-renewable option would be quite high when compared to the low cost of using gas to heat a well insulated house.

BryanF

Metric Tensor wrote: »

If you are on the gas mains in my opinion it is a no brainer to use gas central heating. The payback period for any semi-renewable option would be quite high when compared to the low cost of using gas to heat a well insulated house.

What about reductions in co2 by being able to use % renewable electricity

Or

A Local wood source..

IMO cost is not the only factor to consider

BoardsMember

Are there things they should be looking at regarding best use of technology in relation to heating thermostats in rooms, centrally controlled, web/app accessible etc

We're planning a refurb and I'm trying to work out what the best approach re heating would be. We have gas fired central heating, condenser boiler, thinking about undefloor downstairs, rads upstairs.

I've read about netatmo, hive, nest, and can't decide that is best. Anyone got any suggestions/recommendations? Sorry for hikacking the thread a bit, but it might add to OP info.

BoardsMember

I found a pretty good review for the automation options here: http://www.pcadvisor.co.uk/test-centre/digital-home/12-best-smart-heating-systems-2016-2017-uk-hive-nest-more-3583499/

Metric Tensor

BryanF wrote: »

What about reductions in co2 by being able to use % renewable electricity

Or

A Local wood source..

IMO cost is not the only factor to consider

A fair point Bryan -

If you are happy to pay slightly more for the sake of a better environment and a cleaner future then it makes sense to include a renewable component in your design.

JonathonS

Re insulation you could also consider pumping the cavity with a closed-cell foam. This will significantly improve the airtightness of your walls. It is more expensive than beads, but a lot less than external.

gooner99

JonathonS wrote: »

Re insulation you could also consider pumping the cavity with a closed-cell foam. This will significantly improve the airtightness of your walls. It is more expensive than beads, but a lot less than external.

Is there not concern that the foam has the potential to spread the wall leading to cracks occurring?

jiggins

gooner99 wrote: »

JonathonS wrote: »

Re insulation you could also consider pumping the cavity with a closed-cell foam. This will significantly improve the airtightness of your walls. It is more expensive than beads, but a lot less than external.

Is there not concern that the foam has the potential to spread the wall leading to cracks occurring?

That is a very real concern. This happened recently in my new build. Cracks at every external corner and some internally. Engineer is comfortable with them and signed off on project but I would go wide cavity and beads next time.
Jiggins

Markcheese

I think I'd get the walls pumped ..just ensure the engineer checks out walls properly... some seventies houses were light on Wall ties ...
On the heating .... I like the idea of air to water heat pumps ... but if you're going to have large open plan areas could you go air to air ??
A friend who built his own house piped for radiators, but didn't install the rads .. because "pipe is cheap" and it keeps his options open for the future...

Andrewcampbell

Andrew