Retrofitting EWI

[Onoff]

And to think until I found this forum I didn't know what EWI stood for!

 

In broad terms is there any point in fitting EWI to an existing traditionally built house say with a suspended timber floor? I'm assuming you would get cold bridging issues up through the walls from the footings?

 

Or is it that you combine it with internal insulation on the walls and floors too?

[Dudda]

Fitting EWI, while costly, is very beneficial to a house as you reduce other cold bridges such as at first floors, internal walls junctions, etc. Nothing you can do will remove the thermal bridge of the wall from the footings however it can be reduced. Extending the external insulation down 300mm or more if you can below ground level externally will reduce the cold bridge. This might require modifying foothpaths around the house etc but in my case I had to relocate rainwater drainage and was digging up footpaths anyway. With a suspended floor you should also be able to insulate the floor easily. Internal insulation will be more disruptive if you're living in the house.

[Onoff]

Cheers. Worth considering then. Modifying footpaths......well on one side of the house it's already gone!

 

 

Next question then, what happens with a soil stack like the one in the picture & EWI ? And drain pipes for that matter.

Edited October 24, 2016 by Onoff

[daiking]

12 minutes ago, Onoff said:

Cheers. Worth considering then. Modifying footpaths......well on one side of the house it's already gone!

 

 

Next question then, what happens with a soil stack like the one in the picture & EWI ? And drain pipes for that matter.

 

Someone posted a great photo of that on GBF the other day, naturally after someone asked about IWI but got mostly EWI advice.

 

But shouldn't you finish the bathroom first?

Edited October 24, 2016 by daiking

[Dudda]

23 minutes ago, Onoff said:

Cheers. Worth considering then. Modifying footpaths......well on one side of the house it's already gone!

 

Next question then, what happens with a soil stack like the one in the picture & EWI ? And drain pipes for that matter.

All pipes, rainwater, SVP, etc have to be modified and brought out. The Electrical box is also extended out along with window cills, etc. You also need to consider all external items which are fixed to the walls like gates, clothes lines, satellite dishes, TV aerials, etc. You can't fix these to insulation later so want to allow grounds same way radiators internally need support. It looks like you have wet dash too which might need a coat of plaster to create a smoother more level base for the external insulation. You don't want air pockets behind the EWI. It's a big job that needs a lot of consideration. 

[oldkettle]

4 hours ago, Onoff said:

In broad terms is there any point in fitting EWI to an existing traditionally built house say with a suspended timber floor? I'm assuming you would get cold bridging issues up through the walls from the footings?

 

 

When you say traditionally, do you mean cavity walls or solid walls?

[Onoff]

4 minutes ago, oldkettle said:

 

 

When you say traditionally, do you mean cavity walls or solid walls?

 

In the words of Ms Minogue "I should be so lucky!".

 

The elevation in the photo has one solid brick wall nom 300mm thick then the bathroom wall which is a later added cavity wall.....that's a mix of brick and breeze. Other elevations are solid brick then 9" block. Even the external render is different. The only thing consistent is the paint colour on the wall.

[Onoff]

2 hours ago, daiking said:

 

Someone posted a great photo of that on GBF the other day, naturally after someone asked about IWI but got mostly EWI advice.

 

But shouldn't you finish the bathroom first?

 

Gay Best Friend?

 

Got a link?

 

Yes I really should get back onto the bathroom I suppose!

[Onoff]

2 hours ago, Dudda said:

All pipes, rainwater, SVP, etc have to be modified and brought out. The Electrical box is also extended out along with window cills, etc. You also need to consider all external items which are fixed to the walls like gates, clothes lines, satellite dishes, TV aerials, etc. You can't fix these to insulation later so want to allow grounds same way radiators internally need support. It looks like you have wet dash too which might need a coat of plaster to create a smoother more level base for the external insulation. You don't want air pockets behind the EWI. It's a big job that needs a lot of consideration. 

 

Cheers. All excellent info. If I'd have known what I do know I'd have made provision to drop the soil internally and out under the foundations. Hindsight eh! Tbh if ever I get around to it I'd sand blast all the paint off the (bulletproof) render and re-render it flat. Drives me nuts the present varying finish.

Edited October 24, 2016 by Onoff

[daiking]

15 minutes ago, Onoff said:

 

Gay Best Friend?

 

Got a link?

 

Yes I really should get back onto the bathroom I suppose!

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14627&page=1#Item_21

 

post by gravelld about halfway down, great pictures.

[oldkettle]

17 minutes ago, Onoff said:

 

In the words of Ms Minogue "I should be so lucky!".

 

The elevation in the photo has one solid brick wall nom 300mm thick then the bathroom wall which is a later added cavity wall.....that's a mix of brick and breeze. Other elevations are solid brick then 9" block. Even the external render is different. The only thing consistent is the paint colour on the wall.

 

The reason I asked is my existing walls are cavity so I am interested as well :-)

 

[j_s]

I go back and forth on whether I should do this. Detached 4 bed house with 75/80mm full insulated wool batts. I have various draughts which are hard to track down which this would help with. I can only do 100mm max though due to moving waste pipes and narrowing of walk way down the side of the house, kitchen waste pipe being the major issue as it would narrow the walk way down to much to get the wheelie bin down there and this is a must. Is it wise to have different thicknesses of ewi on different walls. For example 50mm or less on the east facing, 100mm on the rest?

 

I know I won't get the money back but we like where we live and it's about comfort more than anything 

[Onoff]

It appeals to me more and more and had I had the experience of this site (and eBuild before) I might have gone that route initially. Doing my bathroom it never ceases to amaze me how draughty the walls are. Even though they're rendered inside as I work my way round, battening, insulating between and putting a VCL over the lot the draughts are more noticeable where I haven't done. Round the window, old soils & wastes, cracks even. EWI might have saved me lots of work the but it was all a bit alien when I started!

 

 

 

[j_s]

I've just done work around soil pipes today with foam. Generally there are no obvious draughts from the internal block work. I'm sure there will be some like where a TV aerial cable was routed through from the conservatory back to the lounge so they went out through the external wall of the conservatory and in through the external wall of the lounge. No silicone or grommets just a nice hole for air to rush through. I wouldn't mind but the conservatory is attached to the lounge so they could have routed it internally!

Edited November 5, 2016 by j_s

[Onoff]

Expanding foam on its own imo is a bit shite tbh. OK as a "filler". I core cut a bit of Celcon to block this old soil up. Wetted it and used quality gun grade Soudal expanding foam. When dry I could feel "pin point" draughts. I think it's more through the breeze blocks than the fault of the foam. I finished this off with Fischer 2-part chemical resin.

 

 

[Onoff]

Is there any point in doing retrofit EWI piecemeal? By that I mean elevation by elevation. Would it improve heat loss issues with each bit done? 

[Crofter]

It will make a bit of a difference, but you really need to do the whole house. Heat loss will be greatest where there is the greatest temperature difference- hot walls lose more heat. So you effectively shift the heat loss to a different point. A 100mm layer of EWI on one wall won't have anywhere near the same impact as that same material spread more thinly across every wall. A bit like how you can wear as thick a wooly hat as you like, of the rest of you is naked you'll still freeze your nuts off.

[Ferdinand]

I have just done a reasonably extensive IWI refit which might be a useful point of comparison.

 

In this case I looked at EWI but the quotes came in at 14k for the whole thing (small but long 3 bed semi), which was EWI on the gable and the back plus IWI for the front room and bedroom because ornamentation prevented EWI.

 

For the rented property that would swallow 6 or 7 years of profit by the time other necessary works had been done, so we went IWI instead, which is summarised below.

 

There is a long thread about options and debate called The Landlord's Energy Dilemma over at GBF:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14688&page=1

 

Quote

 

Quote

Thanks for all the help here. I have included most details below, though I am sure some of us could have beaten my sourcing. 

The Reckoning.

The final project, after T identified a damp issue when stripping back to redecorate, involved: 

1 - Boarding out approx 45 sqm of wall. Using CLS, 50mm celotex, vapour membrane, 12.5mm plasterboard. Actually used 30-32sqm of celotex and ~42 sqm of plasterboard. That is the clue that about 30% of the insulated walls are doors or windows.
2 - Loft insulation to 300 or 400mm.
3 - Fitting PIV fan and replace bathroom / kitchen extractors. Shaving 10mm off a couple of doors to help air circulation between rooms.
4 - A range of bits and pieces as required, such as pipe lagging in loft, CO alarm etc.

Ventilation:

Nuaire PIV Fan: £290
Airflow Icon 25 extractor fan with shutters for bathroom: app. £100 incl. timer overrun module.
Vent Axia Lo Carbon Tempra P HR Extractor Fan for kitchen: £150

* Loft

Insulated existing loft hatch (celotex cutoffs plus piping).
Loft insulation to be done free to 270mm. £20 survey charge. May be an extra charge if I ask for 370mm or 440mm.

* Boarding Out

Done traditionally with battens not dot and dab so that there are places to hang things if required. 50mm celotex. Vapour membrane. 12.5mm plasterboard.

50mm celotex: 1200x450 from B&Q @ £3.40 each (offer now ended) approx 60 off ~£6.30 per sqm. Equivalent to £18 for an 8 x 4 heet.

CLS 38x63mm 2.4m approx 60 off. Wickes @1.89 each. 

Plasterboard: 1.8 x .9m small sheets from B&Q approx 25 off. For ease of handling. Approx £4.60 each = £3.00 per sqm.

Plaster skim: £350

Vapour membrane. Wickes basic roll. One @ £18.

* Incidentals 

Various incidentals done because it was silly not to, eg sockets replaced single to double if it needed moving out.
Radiators put into 300mm flexi hoses.
Expanding foam and plasterboard screws.
Pipe lagging.
CO alarm for boiler in loft now that there is an air intake up there.
etc.

I will also be rebating a portion of one month's rent for disturbance as we did not see this coming, and covering deorative materials paid by T that are now behind the boarding.

*Totals

Roughly £1000-£1100 on materials and kit.
Plus 10-12 days or so of time, including a couple of days from me.
Plus Plasterer.
Plus partial rent rebate etc and replacement wallpaper etc.

So total cost is something like £2.5 - 3k. Call it 2.5k without the rebates to the tenant.

I do not see how that could sensibly have been much more economical.

* Estimated Viability 

Existing EPC score is 54 for Efficiency = very top of E.

Existing 2015 EPC estimates energy costs as £1200/yr, which I think is little low - long thin house. For T I estimate the expected bills to be £1500-1600 / year or 1200-1300 if they get the correct tariff.

Normal sources of heat loss are taken to be 25% roof and 35% walls in a pre-insulated house.

The EPC suggests that potential savings are £350-400 per year through EWI/IWI and doesn't mention loft insulation. 

We have boarded out approx 65% of the external walls of the main rooms / bedrooms (kitchen excepted), and half of the rest is chimney breast, heavily insulated the loft, and reduced humidity with a Heat Recovery ventilation. 

So I am estimating saving 50% of the possible through the wall savings estimated by the EPC (they say £349 so £175) for insulating plus half of the heat lost through the loft (say 12.5% of £1400 per year = £175). 

On the loft we have increased insulation significantly. For the walls we have not done a complete job and only given those parts insulated a u value of around 0.35-36 (render, 225mm brick, plaster, 10-12mm airgap, 50mm celotex with approx 12% 63mm battens by area sans airgap, 12.5mm plasterboard, skim).

So I make those savings at 30% of heating bills or approx £350-370 a year or £30 a month to the tenant.

Crude payback period is around 7-8 years, which is OK, and I am looking for T energy bills to be under £1000 if they move their tariff. I might get an extra £10-15 a month of rent as my share of that saving when we adjust the rent in 3 years, if Ts have been educated by their lower bills.

As LL my main way to get that 2.5 to 3k back is if I avoid 2 changes of tenant, ie treble length of tenancy, which tend to cost £1000-2000 each around here, considering recruitment charges, void losses, admin and paperwork, and property maintenance. This T redecorated themselves, which is my preferred make-it-simpler-for-everyone approach when they have a dog.

I think I may do an EPC, just to see how far it gets and lock in the evidence. I think it will go well into the Ds but will perhaps need a new boiler and room thermostats to reach a C.

That's all folks, and is my best current solution to the Dilemma of the title. 

I'm happy to try and answer any detailed questions.
 

 

 

If ECO funding was still in place for EWI I might have done it, as it would have been under 10k.

 

The IWI scheme with other bits worked out at about 3k, and the tenant is buzzing about it having had a couple of weeks of Cold House first.

 

The Deilemma of the title is that I have done the investment but the Tenant gets the saving, which is less problematic that the Green Deal where the T pays for my investment but still not ideal.

Ferdinand

 

Edited January 6, 2017 by Ferdinand

[Ferdinand]

12 hours ago, Onoff said:

Is there any point in doing retrofit EWI piecemeal? By that I mean elevation by elevation. Would it improve heat loss issues with each bit done? 

 

IMO yes, but you need to think first about the whole thing and decide your spec, plan and budget first - which should be reasonably consistent.

 

You can either do a big bang, or in bits as appropriate.

 

You really want to make sure you do our glazing first or mount it in the EWI, and need to give thoughts about dealing with the cold bridge you may be creating in the entire thickness of all your walls at the top if you don't EWI the gable, and your gable becomes a radiator. Room in roof insulation is the best solution there or your free loft insulation plus stick slabs of PUR to the gable inside your loft to lower the EWI temp gradient in the wall.

 

If you do go IWI remember the slice of wall between your Ground and First floors, and window reveals.

 

One thing about EWI is that the govt is planning something soon, but are still at the waffle and standards stage.So look into that. Last time grants were two thirds of the first 6k but they needed to be able to apply EWI to most of the house. Get yourself on a waiting list at some of your local suppliers to be contacted. Or do some modest IWI and make sure that the assessor misses it if you EWI later.

 

See https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/578749/Each_Home_Counts__December_2016_.pdf

 

Also an issue for you will be sealing the cavity or your EWI will be useless if it is open to some degree to the outside - in which can you may as well put the EWI on the garden wall :-) .

 

Ferdinand

Edited January 6, 2017 by Ferdinand

[gravelld]

13 hours ago, Onoff said:

Is there any point in doing retrofit EWI piecemeal? By that I mean elevation by elevation. Would it improve heat loss issues with each bit done? 

Yes, in fact for most it's probably the only way it can be done due to cost.

 

See http://europhit.eu/

 

5 hours ago, Crofter said:

It will make a bit of a difference, but you really need to do the whole house. Heat loss will be greatest where there is the greatest temperature difference- hot walls lose more heat. So you effectively shift the heat loss to a different point. A 100mm layer of EWI on one wall won't have anywhere near the same impact as that same material spread more thinly across every wall. A bit like how you can wear as thick a wooly hat as you like, of the rest of you is naked you'll still freeze your nuts off.

 

The trouble with that is, you just end up with the house done to not as good a standard as could be done, so large opportunity cost.

 

I suppose it depends how long the house will be standing afterwards.

Edited January 6, 2017 by gravelld

[gravelld]

1 hour ago, Ferdinand said:

One thing about EWI is that the govt is planning something soon, but are still at the waffle and standards stage.So look into that. Last time grants were two thirds of the first 6k but they needed to be able to apply EWI to most of the house. Get yourself on a waiting list at some of your local suppliers to be contacted. Or do some modest IWI and make sure that the assessor misses it if you EWI later.

 

...

 

Also an issue for you will be sealing the cavity or your EWI will be useless if it is open to some degree to the outside - in which can you may as well put the EWI on the garden wall :-) .

 

Do you think these schemes will allow best practice like:

 

- Insulating down to foundations

- Installing windows in the insulation layer

- Taping and sealing correctly

- Consideration to ventilation requirements of the property

 

? I'm a bit cynical about that. Whenever I see existing ECO work it looks like it has been done as fast as possible, plinths left exposed, cold bridges at windows, then a whacking great air brick because someone got worried about ventilation and no-one thought to design that in.

 

And regarding cavity walls, don't even think about sealing cavities after insulating the external skin on government schemes; according to these schemes, anyone with a cavity wall has good enough insulation already (nonsense of course).

Edited January 6, 2017 by gravelld

[Onoff]

Didn't the ROI government spend millions retro fitting housing stock whilst at the same time creating jobs?

[Ferdinand]

29 minutes ago, gravelld said:

 

Do you think these schemes will allow best practice like:

 

- Insulating down to foundations

- Installing windows in the insulation layer

- Taping and sealing correctly

- Consideration to ventilation requirements of the property

 

? I'm a bit cynical about that. Whenever I see existing ECO work it looks like it has been done as fast as possible, plinths left exposed, cold bridges at windows, then a whacking great air brick because someone got worried about ventilation and no-one thought to design that in.

 

And regarding cavity walls, don't even think about sealing cavities after insulating the external skin on government schemes; according to these schemes, anyone with a cavity wall has good enough insulation already (nonsense of course).

 

Those are *excellent* questions @gravelld.

 

Quote

And regarding cavity walls, don't even think about sealing cavities after insulating the external skin on government schemes; according to these schemes, anyone with a cavity wall has good enough insulation already (nonsense of course).

 

That may skewer my comment because they traditionally view EWI as a solution for "hard to insulate" which normally means solid walls. I am not sure what they do with non-fillable cavaties eg 45mm cavities from  something built in say 1925.

 

Over the years I have had several quotes and surveys, and those have been on solid walled houses with one on a narrow cavity house which was declared ubsuitable for  cavity-wall insulation.

 

Quote

Do you think these schemes will allow best practice like:

 

- Insulating down to foundations

- Installing windows in the insulation layer

- Taping and sealing correctly

- Consideration to ventilation requirements of the property

 

I think those should be OK, although the default will be building regs minimum.

 

As it is basically a cash grant up to X amount, if you choose to have a gold-plated solution at your own extra expense that is no skin off their nose unless your entire scheme falls within the limit, which probably means mid-terraces only, when it would be more complex. It will all be in the initial conversation.

 

The quote I mentioned above was in December 2016, and still included a very small amount (5% ish) of funding. Their spec was U value of 0.29, but they were happy to quote for 150mm rather than 90mm EPS, and the minimal funding was still in the quote.

 

I had a long chat with the head of BS (=Building Standards) at my local council, and his key point was to check previous jobs and to supervise and enforce detail to the nth degree.

 

Ferdinand

 

Edited January 6, 2017 by Ferdinand

[Onoff]

Insulating below footings shouldn't be a huge drama as I plan taking the external paths up anyway for one reason or another and the footings aren't that wide.

 

Another pipe dream probably. After the bathroom it's either the roof or knock through the lounge & dining room. Different ceiling and floor heights, the walls are offset one room to the other and of differing construction! Business as usual then.

 

Didn't the ROI government spend millions retro fitting housing stock whilst at the same time creating jobs?

[gravelld]

14 minutes ago, Onoff said:

Didn't the ROI government spend millions retro fitting housing stock whilst at the same time creating jobs?

 

Government could do it, it just depends what it wants to spend its money on. But we're talking many billions nationwide. Would you rather have HS2 or healthy homes? I think I know which one would benefit productivity and ease the strain on the NHS more.