Opinions on insulation

ONY · 19-05-2021 9:36am #1

Hi, Renovating a detached bungalow built around 2001. 100mm cavity walls with 50mm insulation. Roof insulation will be upgraded along with all windows and doors. Inside is plasterboard blobbed on to bare block.

We are considering dry lining for now with up to 100mm on battens. With a view to possibly pumping and wrapping the walls externally later on. What option would you take for wall insulation?

sydthebeat · 19-05-2021 9:41am

ONY wrote: »

Hi, Renovating a detached bungalow built around 2001. 100mm cavity walls with 50mm insulation. Roof insulation will be upgraded along with all windows and doors. Inside is plasterboard blobbed on to bare block.

We are considering dry lining for now with up to 100mm on battens. With a view to possibly pumping and wrapping the walls externally later on. What option would you take for wall insulation?

sounds like you will be subject to TGD L 2019 "major renovations" and therefore will need to comply with this in all aspects.

you need to get a DEAP assessment done which will provide you with a specification of what you need to do to comply

MicktheMan · 20-05-2021 1:16am

ONY wrote: »

Hi, Renovating a detached bungalow built around 2001. 100mm cavity walls with 50mm insulation. Roof insulation will be upgraded along with all windows and doors. Inside is plasterboard blobbed on to bare block.

We are considering dry lining for now with up to 100mm on battens. With a view to possibly pumping and wrapping the walls externally later on. What option would you take for wall insulation?

Air tightness should be a priority.

Calahonda52 · 20-05-2021 9:19am

as above plus get windows and EWI does together, with new windows hung on outside leaf for near zero cold bridging

Penn · 20-05-2021 9:28am

I think it'd be a mistake to dryline now, then externally wrap later on with/without pumping the cavity. Your insulation is always best in one continuous layer. If you dryline now, you'd be better off removing it later. I'd be inclined to push external insulation now if possible. That way you can still utilise the thermal mass of the wall internally to hold in further heat.

Not to mention that for external insulation, you need to ensure it can meet the roof insulation for thermal continuity and prevent cold bridging, so allowing for it now will form your thermal envelope from the start, and will also mean you may not need to pump the cavity either (though it'd help limit thermal bridging too).

Calahonda52 · 20-05-2021 11:43am

well said Penn:)

ONY · 20-05-2021 2:03pm

Thank you for the replies. We did have a survey done and we were advised to plaster the block work and pump the walls. Haven’t heard many good reports about pumping the cavity at all, and we would be reluctant to just do that without any dry lining at all.

Ideally we would get cavity pumped and then EWI but I’m not sure we can manage it in the current budget.

Calahonda52 · 20-05-2021 2:57pm

IMO, pumping a partially filled cavity is bs

ONY · 20-05-2021 6:43pm

Penn wrote: »

Your insulation is always best in one continuous layer. If you dryline now, you'd be better off removing it later. I'd be inclined to push external insulation now if possible.
.

Hi Penn, What would you suggest on the inside walls in the above case please?

Penn · 20-05-2021 7:50pm

ONY wrote: »

Hi Penn, What would you suggest on the inside walls in the above case please?

If you insulate externally, you don't need internal insulation. You can just slab or skim the walls. With the walls insulated externally, the blockwork can absorb internal heat more and releases it slowly back into the house (thermal mass). That's why insulating both internally and externally is redundant.

Internal insulation is cheaper, but keeps the heat within the space only. External insulation is more expensive, but allows the building to absorb the heat and release it back into the house over time, meaning you require less heat/energy overall. Doing both means you get the benefits of neither.

ONY · 20-05-2021 11:10pm

That is very helpful - thank you for such a comprehensive reply.

rn · 21-05-2021 7:20am

The other problem of putting in two layers of insulation, you might be creating an ideal environment for not nice stuff to grow. The block or material between the insulation layers can't breath, it's dark and especially if moisture gets in somewhere, it's not good. So yet another reason to go with one layer of insulation and do that one layer well.

There's a couple of advantages to external insulation in your case. The two layers are separated by a cavity, so the outer layer of blocks can breath. The insulation is on the outside of the house, so if it's performance starts to go in 20+ years, it'll be easier to repair /upgrade. You will be able to eliminate or greatly reduce cold bridging - another cause of not nice stuff growing due to condensation that arises where cold bridges exist. And there's no reduction in size of rooms internally.

micar · 22-05-2021 9:45am

I got the my house (semi d) externally insulated about 8 years ago.

I am nearly sure that my neighbour insulated both internally and externally about 2 years ago.

Was planning to internally insulate the house. I've already stripped the bedrooms back to the blockwork.

Besides what been said here, I cannot find anything online about the negative impact of both being done.

BryanF · 22-05-2021 9:52am

Why would you need to dry line if if the ewi is done?

listermint · 22-05-2021 10:18am

All to often I think people run after the wrong approach because the results aren't what they expected. E.g getting ewi done I won't have to run my heating at all. Or the house will be instantaneously warm night and day difference.

The do the wrong things and throw bad money after good.

With EWi it can quite easily defeated by poor air tightness into a cold attic space.

Also the impact of an attic gable especially on a bungalow into the rooms below which will essentially wick the stored heat right out of that room. Has people question why they did EWI in the first place.

A real holistic look at entire envelopes has to be done and no single solution actually gives you that silver bullet. There's a case to be made for dryling a gable attic or room below wall if the attic space is a cold one. But you wouldn't dryline other walls as it removes the ability to store heat in them with externally EWI holding it back.

Ewi is great but all other aspects to assist it must be looked at and addressed.

rn · 22-05-2021 4:26pm

Actually I've that gable end problem with my house. Have to say we haven't noticed it, but it stacks up theres a cold bridge into a cold area. You'd nearly need a row of thermo block at ceiling height or make the attic a warm space to counter it.

listermint · 23-05-2021 12:19am

rn wrote: »

Actually I've that gable end problem with my house. Have to say we haven't noticed it, but it stacks up theres a cold bridge into a cold area. You'd nearly need a row of thermo block at ceiling height or make the attic a warm space to counter it.

You'd definitely have to to either or.

I wrapped my house in 200mm two years ago. Had the cavitys pumped first before i started. But did notice specific rooms as colder. The kitchen especially as it contains two chimney stacks either side. Both have been blocked up but the block work itself even though it's behind plasterboard would wick heat. Learned from this and warmboarded the new master bedroom which has a large gable wall . That room is very warm even though it's the north end of the house.

Eventually will convert the attic space so will solve the other rooms at that point.

chooseusername · 23-05-2021 6:45am

listermint wrote: »

All to often I think people run after the wrong approach because the results aren't what they expected. E.g getting ewi done I won't have to run my heating at all. Or the house will be instantaneously warm night and day difference.

The do the wrong things and throw bad money after good.

With EWi it can quite easily defeated by poor air tightness into a cold attic space.

Also the impact of an attic gable especially on a bungalow into the rooms below which will essentially wick the stored heat right out of that room. Has people question why they did EWI in the first place.

A real holistic look at entire envelopes has to be done and no single solution actually gives you that silver bullet. There's a case to be made for dryling a gable attic or room below wall if the attic space is a cold one. But you wouldn't dryline other walls as it removes the ability to store heat in them with externally EWI holding it back.

Ewi is great but all other aspects to assist it must be looked at and addressed.

Not to mention cold being wicked up from foundations in older houses
that don't have the insulating blocks at dpc level.
EWI is not the panacea in all cases.

rn · 23-05-2021 8:26am

It's not a panacea, but is superior to doing interior walls, probably in proportion to its more expensive cost. It's challenging enough to build perfect insulated envelope from scratch, It is impossible to retrofit perfect solution.

And while any improvement in insulation is good, they have to he put together in the right way to get bang for buck... And you'll still have a heating bill. Lol.

ONY · 23-05-2021 9:20am

I’m guessing a hipped roof doesn’t pose the same problem as the block work is completely covered with EWI?

MicktheMan · 23-05-2021 3:21pm

ONY wrote: »

I’m guessing a hipped roof doesn’t pose the same problem as the block work is completely covered with EWI?

Correct, but hipped roofs pose other challenges at ceiling level in external corners

ONY · 15-08-2021 10:00am

Back again, we’ve now opened the cavity and can see there is 50mm of polystyrene in the cavity but it’s not great. Fairly broken up and lots of cement from the block work. We were planning on pumping the walls then wrapping. Pumping doesn’t seem to be an option now, so we are back to dry lining or EWI leaving the cavity as is. Bare block work has been sand and cemented.

There is so much conflicting advice that I’m not sure which option will work the best. Will externally insulating create a thermal loop in our case and we should therefore dry line instead?

Opinions on insulation

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