Old house insulation hack

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 Mark Edwards 08 Jun 2022

I’m adding internal insulation to my 130 year old solid stone built cottage. It currently has a smart home system (and all the additional wiring that goes with it) but I guess any new owner will want/need to revert it back to standard wiring, so the mods I am making are taking a rewire into account. As I am adding 500mm of insulation to the walls (1000mm in the ceiling), that means I can bury 500mm trunking (and conduit) into the build. The upstairs room in the photo is the one nearest the distribution board. I have installed the trunking at floor level so that the trunking can serve downstairs as well (when I get around to it). The sole plate (bottom woodwork) is above the trunking and supported using (heavy duty) steel ‘L’ straps that are normally used to secure the sole plate of a roof, to the wall, before the joists are added, so are well up to the job. The trunking will eventually be covered with the skirting board so when a rewire is required it can be removed to access the trunking instead of lifting floorboards and chasing walls. So that’s one room almost done, just 3 more to go. Oh, the joys of being retired (for the first time in my life, having the time AND the money at the same time) and having a hobby (making it good for the next generation).

Post edited at 14:38

3
 Moacs 08 Jun 2022
In reply to Mark Edwards:

>  As I am adding 500mm of insulation to the walls (1000mm in the ceiling)

You must have high ceilings for a cottage

 montyjohn 08 Jun 2022
In reply to Moacs:

> You must have high ceilings for a cottage

I assumed he's a hobbit

 David Riley 08 Jun 2022
In reply to Mark Edwards:

You mean two inches and four inches ? 

5
 flatlandrich 08 Jun 2022
In reply to Mark Edwards:

I don't want to throw a spanner in your works but will the uninsulated metal trunking not act as a cold bridge between the outside wall and the warm inside and therefore run with condensation in the cooler months? Dito the metal back boxes? 

Also if your going to that extent why not do the whole thing with PIR board as it's a far more effective insulator than polystyrene?

 ExiledScot 08 Jun 2022
In reply to Mark Edwards:

Assuming you've not retired at the age of 25 why, oh why, did you say hack?

PS. Good work on the insulation, it's a good chance to rethink socket location and heights, plus also put in conduits so you can plug in IT or TV direct into routers. 

2
 ExiledScot 08 Jun 2022
In reply to David Riley:

> You mean two inches and four inches ? 

I was thinking 1000mm is quite a lot of ceiling insulation. 

 daWalt 08 Jun 2022
In reply to Mark Edwards:

Good effort. I hope you've done all your research on the potential pitfalls of this type of thing. 

There's a good point above about cold bridging. 

As long as the gap between the insul and the external wall can shed moisture quicker than it comes in youll be fine. Even with all the vapour barriers and tape, good ventilation is highly recommended (essential if you ask me) 

OP Mark Edwards 08 Jun 2022
In reply to montyjohn:

LOL. It’s above the current ceiling level. I can’t add insulation in the attic as ....   . It’s boarded out. It used to be used as a 'hydroponic experiment'. It kept me in credits during my sabbaticals.

 montyjohn 08 Jun 2022
In reply to Mark Edwards:

> It used to be used as a 'hydroponic experiment'. 

I knew it. Definitely a hobbit!

OP Mark Edwards 08 Jun 2022
In reply to flatlandrich:

Damn. Good point. Being an old house there is no such thing as a straight line, so there is some space behind the insulation. I decided not to use a vapour barrier. Perhaps that was a mistake.

OP Mark Edwards 08 Jun 2022
In reply to ExiledScot:

> Assuming you've not retired at the age of 25 why, oh why, did you say hack?

I was hacking sites (with the help of bulletin boards in the 80’s). Other than doctors surgery’s  what could I have done with 20 tons of nitrogen? It was mostly for giggles and to see what you could see (at 300 baud).

OP Mark Edwards 08 Jun 2022
In reply to ExiledScot:

>put in conduits so you can plug in IT or TV direct into routers. 

Double satellite lines and Ethernet already accommodated (right of vertical on RHS next to socket).

 ExiledScot 08 Jun 2022
In reply to Mark Edwards:

> >put in conduits so you can plug in IT or TV direct into routers. 

> Double satellite lines and Ethernet already accommodated (right of vertical on RHS next to socket).

Full marks.

I'd slap in an empty conduit in reserve going up to loft space etc.. future proofing. Or anything that might bedrooms or home office. 

 daWalt 08 Jun 2022
In reply to Mark Edwards:

> I decided not to use a vapour barrier. Perhaps that was a mistake.

not necessarily - but the void behind the insul needs to be well ventilated top and bottom.

OP Mark Edwards 08 Jun 2022
In reply to ExiledScot:

> I'd slap in an empty conduit in reserve going up to loft space etc.

On the left of the pic there is trunking leading to the attic. I found some (pre wired) lighting distribution panels (that I’ve fitted in the attic) so that the lighting power and switch can be wired to that instead of being in the ceiling rose. OK, it’s costly in wiring but simpler to install and still meets the requirements.

>daWalt

Being a old house the walls are nowhere near flat/square so there is space behind the insulation. I did wonder about cold dropping down from the attic into the ceiling void but figured the ventilation wasn’t a bad thing and will stuff the downstairs ceiling void with rockwool when I get to do downstairs.

 daWalt 08 Jun 2022
In reply to Mark Edwards:

bit unsure about what you mean, but it doesn't matter much. sorry if this is preaching to the choir, but I'll run through it anyway.

even if you add a vapor barrier and tape up everything two things that join together, there will always be some air leaking through from the warm side to the cold. when it does it dumps it's moisture as it cools. ideally the less moisture the better (vapour barrier etc.) but there is no substitute for ventilation.

air moving through the gap between the insulation and the external wall will take moisture away. you want a decent flow of air (you almost can't have too much) and don't want any dead-space where pockets of air have no through-flow. ideally need vents top, bottom, side to side etc.

In reply to montyjohn:

> Definitely a hobbit!

A bong-addled hobbit...

 Sam W 08 Jun 2022
In reply to Mark Edwards:

Good idea. 

For anyone else thinking of adding insulation to old buildings, I found this link useful https://historicengland.org.uk/advice/your-home/saving-energy/making-change...

Although I did a couple of walls in our house with PIR board in stud and a ventilated air gap behind, and it has worked well, I think if I were doing it again I'd look closely at wood wool boards and a lime plaster skim.  I'm a big convert to restoring breathability to stone walls.  I also prefer the feel of lime plaster to gypsum, somehow a bit softer.

 pec 08 Jun 2022
In reply to Mark Edwards:

> I am adding 500mm of insulation to the walls (1000mm in the ceiling),

Seriously?

That's half a metre thickness of insulation on your walls and a metre in the ceiling.

How big are the rooms that you can lose half a metre off one or more walls?

Le Sapeur 08 Jun 2022
In reply to Mark Edwards:

I was with you all the way to the word 'hack'.

 montyjohn 09 Jun 2022
In reply to Le Sapeur:

So you lost him at the title.

Are people really bothered by the word hack?

For me it's acronyms. Lol (especially when not responding to something funny), omg, iirc, and the worst, when reading stuff as a parent dd and ds.

 Phil79 09 Jun 2022
In reply to pec:

> Seriously?

> That's half a metre thickness of insulation on your walls and a metre in the ceiling.

> How big are the rooms that you can lose half a metre off one or more walls?

I assume OP meant 50mm and 100mm....

OP Mark Edwards 09 Jun 2022
In reply to Phil79:

Yes, my mistake.

 Neston Climber 09 Jun 2022
In reply to Mark Edwards:

Looks like a proper job. Make sure you leave instructions somewhere (fuse box) so that future house owners know about the trunking/conduit as I can imagine it not being found until their electrician has sliced up the walls. From experience they prefer to cut quickly and clock off early leaving a plastering job rather than investigate! You never know if you will be around or capable of 'briefing' the new owner and serveyers are never going to look behind a skirting board. 

1
 jiminy483 09 Jun 2022
In reply to daWalt:

> bit unsure about what you mean, but it doesn't matter much. sorry if this is preaching to the choir, but I'll run through it anyway.

> even if you add a vapor barrier and tape up everything two things that join together, there will always be some air leaking through from the warm side to the cold. when it does it dumps it's moisture as it cools. ideally the less moisture the better (vapour barrier etc.) but there is no substitute for ventilation.

> air moving through the gap between the insulation and the external wall will take moisture away. you want a decent flow of air (you almost can't have too much) and don't want any dead-space where pockets of air have no through-flow. ideally need vents top, bottom, side to side etc.

When I did this my building  inspector told  me to build the stud wall 2 inches off the existing wall and tie it in with the ceiling and floor so the two walls don't touch one  another at all.

OP Mark Edwards 09 Jun 2022
In reply to daWalt:

Thanks, that’s helpful. The studwork is 65mm x 40mm so behind the insulation there will be at least a 15mm gap. As the walls aren’t flat there is also a gap between the studwork and the wall (up to about 20mm at the worse point) so that should ensure there are no dead spaces. As the central heating pipes run through the floor, the air there will be warm so I won’t try to plug the gaps so it can rise up to the attic (and take any damp with it). Which makes me wonder if I should use insulated plasterboard on the downstairs ceilings to remove a possible cold barrier.

I can see downstairs is going to more of a problem (but I only need to do the front and back walls as the extension covers the side) and would  have to add vents which seems to defeat the object, but as that’s going to be next year I have some time to think about it. Sam W’s suggestion may well be the solution there, as I already plan to remove the cement render and use lime plaster, so the wood wool boards may be a solution.

1
 Toerag 09 Jun 2022
In reply to Mark Edwards:

On the subject of insulation, I've recently re-insulated the loft at my Dad's house - took out 48yr old very thin rockwool from between the joists, replaced with 100mm recycled PET fluff from B&Q (so nice to use compared to fibreglass) and boarded it all over with 18mm chipboard. My Dad was moaning about the cost of electric going up (he's had his oil boiler replaced with electric) so I finally got round to doing the calculations and the amount of energy saved over a virtually uninsulated ceiling is massive. He's a bit happier now!

 Philip 09 Jun 2022
In reply to Mark Edwards:

Isn't such a material change in the building subject to building regs and inspection? Will they be happy with the metal conduit at the bottom and the impact that has on thermal insulation?

https://www.planningportal.co.uk/permission/common-projects/roof/building-r...

In reply to Mark Edwards:

Forgive me if I have misunderstood your intentions, but isnt trunking at the bottom of a wall out-of-zone for concealed cabling?

As I understand it, putting skirting over without mechanical protection wouldn't meet regs 

In reply to SpaceCaptainTheodore:

Ah bum - just realised you have 50mm+ depth. Ignore me.

 pec 09 Jun 2022
In reply to Mark Edwards:

> Yes, my mistake.

I imagined it probably was a mistake but thought it best to clarify.

 Fraser 09 Jun 2022
In reply to Mark Edwards:

Was there any particular reason you didn't install dwangs between the studs? I was also wondering if your trunking zone will be forming a cold bridge, I don't quite understand the heavy duty steel angle you've used there for some reason.

 Rampart 09 Jun 2022
In reply to captain paranoia:

> A bong-addled hobbit...

I wondered what 'hydroponic experiment' might be a euphemism for.

 Maggot 09 Jun 2022
In reply to Rampart:

> I wondered what 'hydroponic experiment' might be a euphemism for.

Bill and Ben and .......? 😵‍💫

 ian caton 12 Jun 2022
In reply to daWalt:

Only where there is a gas pipe crossing through.

We did ours 15+ years ago. North facing 1880's solid stone walled back to back 1000' up un the pennines. Void dry as a bone.

I have done other houses. 

What i would say is it is vital the insulation is air tight. As warm air rises internally quite a pressure differential builds up so any small leak makes a massive difference to its effectiveness. 

A worry is floor joists resting in what is now a cold and potentially internally damp wall leading to rot. Hence good idea for internal vapour barrier, foil backed plaster board. Plus spray on external miusture barrier. 

I believe state of the art is to chop the joists and tie them and the wall into a steel running parallel to the wall at floor level. 

 daWalt 12 Jun 2022
In reply to ian caton:

I completely agree, and you're absolutely right about the need for air-tightness; it's the ability to reliably achieve it that I'd be worried about.

for my own peace of mind I'd always add vents because you can't be certain that things won't change in the future. e.g. if you're drilling holes in the wall to put up a shelf it's very easy to drill right through plasterboard, vapor barrier, and insulation. ventilation will be potentially unnecessary, but you've given yourself a bit of redundancy in the event of more than expected levels of moisture getting through.

given the OP's not installed a vapor barrier, I'd say ventilation would be highly recommended in this instance. 

OP Mark Edwards 12 Jun 2022
In reply to Mark Edwards:

To answer some of the points raised.

What’s the problem with the word ‘hack’? The phrase ‘life hack’ is quite common. To me, it seems to mean an alternative way of doing things.

>Fraser

The way I see it is that there are no lateral forces on the structure, so why would I need them? I had cut the dwangs  but didn’t see the need to fit them. The sole plate is screwed to the wall and is supported on brackets that are also screwed to the wall which ensures there is no load on the trunking. The verticals are screwed to wall and the top beam is secured to ceiling rafters and as the structure is on two sides of the room it’s not going anywhere.

>Philip

Damn. I didn’t think that this would come under the jurisdiction of Building Control. I helped a friend do the same sort of  thing and he said that he had checked with Building Control (in a different area) and they said that it didn’t need to be notified. But that was just one wall of a terraced house and from what I have read, doing one small room at a time may get around the regulation. But I don’t want to cause any problems for future occupants (the only way I leave here is in a box), so that is what I am trying to do. I tried to contact my local Building Control but apparently I can’t get to talk to someone before I submit the application and pay the fee. Grrr. It’s not a show stopper as I knew I would need to contact them sooner or later for other work I had planned, so it’s made me re-evaluate my priorities.  So that’s a tidy up of the other work and the smart house capability to be removed. It’s a nice to have, but not essential. I just have to figure out how to make everything dumb again and simplify back to 'normal', as it’s highly unlikely any new occupant would be able modify/maintain it.

>ina caton & daWalt

“A worry is floor joists resting in what is now a cold and potentially internally damp wall leading to rot. Hence good idea for internal vapour barrier, foil backed plaster board. Plus spray on external moisture barrier. 

I believe state of the art is to chop the joists and tie them and the wall into a steel running parallel to the wall at floor level.“

I can’t see where this moisture/vapour barrier would go. Against the wall (seems a really bad idea), on the wall side of the structure, or the room side? The joists look like they are recycled timber (I don’t think they are oak but they are a very tough wood) as they have some incredibly tidy holes in really odd places (i.e the lintels above the windows are about 18” x  3”. Above one window there are two 2” holes at really odd spacing’s and there is a perfectly square 2” hole in the joist half way down the stairs, where you can see the chisel marks). I don’t think they are anything to do with the original gas lighting as they are nowhere near the old lead gas pipes and fittings I removed many years ago. So if they have survived over almost 100 years I don’t think it’s a major concern as I have seen no sign of rot in the ones I have inspected.

 Again, I would like to thank those who have replied, it has given much to think about. As I’m getting building control involved it’s good to know the points that could be raised. It’s a bit like a cheat sheet of the issues that could be raised by the annual NICEIC inspector. I have built the structure using screws and can take it all apart, if something like a vapour barrier needs to be installed. It’s a nice house despite the lack of anything approaching level or flat. Considering the age, I am highly impressed by the skill of the original builder and would like to think that my efforts would be similarly regarded by those with an appreciation of such things. As an example I stripped off all the render in the bathroom to expose the stone. To me, it’s a work of art when you see how it’s constructed.

P.S. As my smart house system is going to be ripped out, does anyone fancy the hardware before I send it to the tip? It’s a CAN system so the interconnects are run over cat5 cable and I have the control software packages too.  It’s not a consumer product (the business model was to sell exclusively to high value developments (a mistake in my opinion)) but some of the components were the default system installed in the One Hyde Park development, as an example. No charge (if you come and collect), but the promise of a donation to a charity would be appreciated. I can’t supply the whole system yet, but have enough spares to supply an evaluation pack (including the important Ethernet interface). And whilst I am here, will answer/assist with any questions.

Post edited at 17:40

OP Mark Edwards 12 Jun 2022
In reply to Mark Edwards:

HA System.


 ian caton 12 Jun 2022
In reply to daWalt:

Fair enough, but he is only adding 50mm insulation to the walls. If those walls are a decent thickness they probs have similar thermal resistance as the 50mm,so venting the cavity cancels out the benefit of the insulation. I think un an old house he will probably get most benefit from the increased air tightness. That's my thoughts anyway. It is easy to put a lot of effort and cost in and be underwhelmed by the result. 

 ian caton 12 Jun 2022
In reply to Mark Edwards:

Building control is required if you change the thermal properties. They are only concerned if you are reducung those properties. They will just nod it through if you are imorovibg. It is, imo, worth doing because it will be recorded as having been done so when you sell it will appear on the epc.

Re vapour barrier. If the pic is if your work you are in fact installing one such. The foil on the insulation is there to stop moisture vapour passing into the colder side of the insulation and condensing there resulting in waterlogged and ineffective insulation. You always position a vapour barrier to stop warm escaping to cold. 

But you need to get foil tape to cover the studs. For the ceiling you buy foil backed plasterboard. If that is polystyrene in the ceiling i would check flammability. Pretty sure it's not good. Phenolic foam is the stuff to have, or fire proif plaster board but then it doesn't come foil backed. 

Not sure what is going on at wall floor junction. But looks like it might be tricky to seal as is. Once studded i would have sprayed all around inside edge with foam before installing insulation. I know too late now but i would have used insulated plasterboard on top of studs. 

Post edited at 22:10
 daWalt 13 Jun 2022
In reply to ian caton:

not from my research into u values:

solid wall - 1.6 - 1.9 W/m2K

50mm PIR - 0.44 W/m2K

1
 ian caton 13 Jun 2022
In reply to daWalt:

Fair enough but it is still worth having, plus the air gap whicj is another 0.5 if my memory serves me well. All negated by venting. 50mm of insulation isn't much. 

 Fraser 13 Jun 2022
In reply to Mark Edwards:

> >Fraser

> The way I see it is that there are no lateral forces on the structure, so why would I need them? I had cut the dwangs  but didn’t see the need to fit them. The sole plate is screwed to the wall and is supported on brackets that are also screwed to the wall which ensures there is no load on the trunking. The verticals are screwed to wall and the top beam is secured to ceiling rafters and as the structure is on two sides of the room it’s not going anywhere.

I'd not be concerned about lateral loading either, I was thinking more from the perspective of fixing the joints at the top of the plasterboard sheets (assuming you'll be fixing it in 'portrait' format) unless your wall height is less than 2440mm. You don't seem to have a stud on the left edge of the wall, it looks like its a vertical section of trunking, so how are you going to fix that left edge of the plasterboard?

I'd also have introduced a vapour barrier for sure. You're changing the breathability & thermal performance of the envelope and the BCO may not like what you've done.

And to be honest, I'm not really clear on what this "smart house system" is that you're describing. Is it just insulation and accessible trunking or am I missing something? I'm not getting a One Hyde Park vibe here at all, sorry!

 Toerag 13 Jun 2022
In reply to Mark Edwards:

>So if they have survived over almost 100 years I don’t think it’s a major concern as I have seen no sign of rot in the ones I have inspected.


 That's because the wall has been heated by the room and thus kept relatively dry. Now your insulated drylining will prevent the heat from the room getting to the wall, and thus there is an increased chance that the wall will become damper because its colder.  There's also the possibility that reduced air circulation in the new wall-stud cavity will increase the humidity in the proximity of the wall.  On the positive side, if your stud wall is well-screwed through to the floor joists and ceiling joists above then when the joist ends rot away it will suspend the floor .


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