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Author Topic: Retro insulation for room in the roof  (Read 1364 times)
Anniemac
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« on: October 01, 2018, 09:53:00 PM »

We have three rooms in our loft. The conversion seems to have been done about 30 years ago. At the moment most of the horizontal and vertical surfaces have some insulation.  I can do the rest of these surfaces and replace the insulation that has been chucked about by others. I also hope to increase the vertical insulation and insulate the hatches.

The diagonal parts of the roof have no insulation. They are about 1.5 meters long and with a bit of effort I think I can get to both ends. There is a W ater tank in the way on one end of the loft so I only want to climb over the tank once! I think there will be noggins on some of the rafters so I will probably need to get to both ends.

I have looked at loose fill but I am not sure how to stop it flowing straight out and also worried about causing ventilation problems because I cannot control the air gap. And the noggins would be in the way.

I have considered insulation board such as kingspan k7.  This would obviously need to be cut to fit but would probably be easier to push into the gaps. I am concerned about the fire risk because the rooms in the roof are bedrooms for our kids.  Do you know the fire resistance or not for these types of insulation.

Also considered Knauf earthwool. This is listed by Knauf as being semi rigid but I am not sure I could push it up the gaps without it catching and snagging.  I am not sure if I can get enough depth and keep 50mm airgap which seems to be the requisite ventilation. Also does it need to be moisture resistant or coated with foil.

Has anyone done this sort of job successfully.  I want to do the diagonals before reducing the access by topping up the other insulation. So I need to get on with it.

Many thanks for any advice.

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kristen
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« Reply #1 on: October 02, 2018, 06:34:43 AM »

Aerogel is thin and "material like" so would "push into the gaps", although not sure that would ensure no cold bridging etc.  Not cheap, and not pleasant to cut
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Barrie
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« Reply #2 on: October 02, 2018, 09:50:25 AM »

Have the work done for you for free...

https://www.moneysavingexpert.com/utilities/free-cavity-loft-insulation/#freeinsulation
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JohnS
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« Reply #3 on: October 02, 2018, 10:07:52 AM »

I would second the use of Aerogel.  One of the most effective insulators for its thickness.  Not cheap, but it works where other materials cannot.

What size are your rafters?  You need a thin insulant as you should retain a 50mm air gap above it.
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heatherhopper
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« Reply #4 on: October 02, 2018, 11:18:02 AM »

Have a similar issue to deal with at some point.
Interested to know what route you take and the result.
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Fionn
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« Reply #5 on: October 02, 2018, 11:47:38 AM »

I know it sounds drastic but I'd be more inclined to gut the place pulling down all the existing plasterboard and start from scratch.
If you try and upgrade it piecemeal it will be very difficult to make it air tight and wind tight which will negate a lot of the value of any of the insulation you install.
I'd put as much rigid foam as you can between the rafters (allowing for 50mm gap), then another layer of foam across that (again as thick as you can do without compromising space), foil tape and install new plasterboard.
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kristen
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« Reply #6 on: October 02, 2018, 01:58:04 PM »

Upgrading existing housing stock is hard Sad

I wish Building Regs required a much, much better starting point - which would then reduce the amount of housing stock that WILL need upgrading during its lifetime Sad
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phoooby
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« Reply #7 on: October 02, 2018, 05:56:29 PM »

I would second taking down the plasterboard to gain access. It is the only effective way would will ensure no gaps and maintain 50mm ventilation. PIR between and beneath and re-board over. The similar areas I have in my house have 100mm between and 50mm beneath based on 400mm centred joists. The bit beneath is required to prevent cold bridging. It will be worth it despite the disruption and mess !.
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kristen
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« Reply #8 on: October 02, 2018, 07:19:04 PM »

It will be worth it despite the disruption and mess !.

Agreed.

I wonder how close folk manage to get to Passive House levels of insulation / air tightness?  I know its a "piece of string question", but I'm curious because I figure its really really hard (unless you get lucky with the starting-point).

My house is more-or-less poured concrete, build in the 60's and relatively airtight as a result. It had a concrete flat roof (since had pitched roof added); masses of insulation added to the loft (which is like a vaulted cathedral, so that was easy), and the cavity filled ...

We've also fitted Aerogel and boards in the window reveals, which has cheered up some cold bridging ...

But the (concrete) floor contains heating pipes and 99% certain there are Asbestos insulated ... but for that I really would have liked to fit UFH ...

The cost to "wrap" the outside was huge (partly because I would want it to look nice ...), so didn't do that. And then all new windows, and move them out - in line with the insulation layer - its a lot to do, and huge disruption.  Sadly, much easier / more tempting just to do a NewBuild ...

I live in hope that improvements in Materials Science will solve this problem for the next generation.
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Anniemac
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« Reply #9 on: October 02, 2018, 10:57:33 PM »

Thank you for all the suggestions and comments.

Our house is 1930s but the builder seems to have built a more arts and crafts house so it doesn’t look 1930s. We have the original brochure for the house where they advertise the modern cavity walls and that you get one electrical socket per room.

The cavity wall was insulated in 2001 and as I said there is some loft insulation but it is the draughtiest house I have ever lived in.  The doors blow open and shut on their own.

In the last house we did pull apart and insulated the walls and roof. But not the suspended floor.  Because they were original parquet and it would get ruined. I also draught proofed really well. That house was toasty.

So starting at the top I need to make sure all of the loft is insulated.

It is never going to be any where near passive house but I can still get it better.

I am not competent to re line the loft rooms and paying for it to be done would never pay back.

Anyway what I am trying to say is like suggested above it’s horse for courses.

I am still researching. I thought about trying a couple of insulation types and seeing what works. Might cost some money but at least I will have an idea of what I can push into the gap. 

Many thanks again


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kristen
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« Reply #10 on: October 03, 2018, 06:16:01 AM »

I missed a couple of things of my earlier list:

Previous owners had fitted uPVC double glazing; first thing we did was cavity fill. That reduced heat requirement, and draughts, but created some damp problems - probably never previously a problem when the house had Crittall metal windows and boiler on 24/7/365 I expect!. Nothing growing as such! but stale air, cold patches, and some damp.

At the time we insulated loft "even better" and insulated the window reveals we also found a way to squeeze in a retro fit of air ducts and MVHR. Given house was already relatively air tight, the only significant "hole" was an open chimney, and we put a passive house style wood burning stove in (which has its own external air supply). The MVHR has revolutionised the air quality, and the damp issue has gone (and coupled with that we lowered the thermostat by a couple of degrees and now keep that part of the house quite cool in winter).

I haven't checked MVHR to see what differential inlet/exhaust temperature are, but there must be some air leakage from the house, maybe more so because it is now under positive pressure, so my expectation is that exhaust volume is less than inlet, and as such heat recovery is not as good as it could be.

(We built a passive house extension at same time, so we "live" in that bit in the winter. Interesting to note that in the 4 years since we did that Wife and I have not had a single Winter cough or cold, whereas always had one in previous winters, and I always struggled to shake mine off; its a known health benefit of Passive House (even temperatures / ducted air I think?) but nice to have had it confirmed, and it wasn't something I even knew of until recently, so definitely not a placebo-effect in my case!)
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kristen
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« Reply #11 on: October 03, 2018, 06:24:20 AM »

It is never going to be any where near passive house but I can still get it better.

If you are not familiar with it might be worth a look at EnerPHit in terms of upgrading / retrofit. My expectation is that getting to Passive House will be neigh on impossible for most existing buildings - particularly, as you say, when folk are faced with totally unreasonable consequences - Asbestos in concrete floor in our case and the sheer cost of an external-wrap (100 year [or whatever!] payback ...), and e.g. " the suspended floor.  Because they were original parquet and it would get ruined." in yours.

https://passipedia.org/certification/enerphit

No idea what it entails though!, I just have heard the word  whistlie
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Anniemac
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« Reply #12 on: October 21, 2018, 05:03:41 PM »

Ok so we have started.

I realised we only have 100mm gap on the slope part of the roof. I went for 50mm kingspan from wickes.  That should give 50mm for ventilation. It was on deal so I got 15% off. Just under £30 per panel. Probably not the cheapest but I only wanted a few sheets.

I have managed to cut and slot in three quarters of the kingspan in the roof from the little side walls. I glued it with gorilla glue but really only to hold it still. I then wedged it while the glue goes off.

I then also realised that the “professional” who insulated the flat loft area in 2001 (they left a sign so if I meet them again I might mention it) didn’t lay the insulation between the joists just across the top with 8-10 inches of air underneath and allowing all the cold air underneath the floor on the second floor. So I lifted the existing insulation put more in between the joists and put the rest back on top.  Could help to explain some of the condensation problems. I also found the extractor fan from the family bathroom with no vent pipe at all just extracting straight onto some manky insulation.

I expressed my disappointment with the situation more than once today.

We had some insulation on some of the side walls so I added more where it was missing and used cavity wall slab over the top.  I used long decking screws to hold it up but I might use something more if it moves.

My better half then cut some kingspan to wedge into the door frame of the bit I have completed. That should help the draughts from the loft door.

I think I have probably spent 12 hours this weekend and will probably need to do the same next weekend to finish it but I hope it will make some difference.

Need to vent the extractor fan before I can do anything more so going to find the best way to get gorilla glue off my hands.

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skyewright
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« Reply #13 on: October 22, 2018, 09:52:14 AM »

I also found the extractor fan from the family bathroom with no vent pipe at all just extracting straight onto some manky insulation.
As you've probably guessed that will have been a major contributor to moisture (& likely condensation) within the loft space.

I speak from experience. We used to get way more condensation in a well ventilated loft than seemed reasonable, even for Skye. It was only when doing some other work that I spotted that some ducting from the bathroom fan had been nibbled through by mice, so the warm wet air was venting directly into the cool loft space.  Sad
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Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40°, WSW, Lat 57° 9' (Isle of Skye)
Fionn
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« Reply #14 on: October 22, 2018, 09:56:11 AM »

The flexible coiled type ducting is a waste of time really, the rigid plastic stuff is expensive but it's done for life once it's installed.
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