Where to get specific advice for retrofitting insulation

terrapinx

I'm living in a 70s chalet style house, so all of the upstairs is in the roof. It's poorly insulated and draughty - there's some fibreglass but also many areas of the roof/eaves/walls with nothing.

I'm looking to put in more solid + soft insulation, and in terms of the work involved + Scottish building regs that all seems fine. But when it comes to the actual design to avoid cold bridges and condensation I'm little more nervous. The house is cold currently but not damp so I don't want to trade one issue for the other.

Is there some expert I could consult to help come up with a plan that I could then execute? If so, who would that be? A surveyor? A roofer? I can afford an hour or two of someone's time to get advice but not for them to do everything.

tacpot12

I would consult an architect. To save time and money, you could prepare some diagrams that show the current construction at each of the critical junctions; the eaves, the ridge, any dormer walls, valleys, etc. You would also need to measure all the critical dimensions, and I would expect them to find some photos useful as well. This would avoid them having to survey the property. 

Ask them to quote for a set of drawings to improve the insulation and airtightness to some specific value. (The building regs might guide you, but you might need to do some further research into air tightness.)

You need to consider what your budget is and tell them this, and also consider whether in improving the air tightness will you cause damp issues that require a mechanical ventilation system. The architect should be able to advise whether such a system would be required, and help specify it, but you should be ready for their question as to whether you can afford such a system (which might be nothing more that a PIV rather than a MHRV), and whether you have the space to install it. 

A surveyor might have some ideas of what would work well, but is not best placed to design the improvements you need. Most builders or roofers would not want to act as a consultant, or have the knowledge to design solutions that would not cause other problems. 

I'd expect a competent architect to work out the design in a day, as there is nothing structural in what you need doing, but producing the drawings will take a bit longer.  You might find an old-school architect who would do some detailed sketches more cheaply than having one of their technicians do CAD drawings.  

terrapinx

Thanks tacpot12, I hadn't even considered an architect. Worried that it's going to be more difficult to do this within budget than I thought, but I'll make some enquiries!

tacpot12

I also had that same worry when suggesting it, which I why I mentioned anything that I thought might help bring the cost down. It just that architects tend to have the knowledge of all the different options for where insulation might be installed. It's part of their training to design houses for airtightness and energy effeciency. All the other professions and trades will know a bit, but not as much as an architect. 

I think it will do no harm to talk to a couple of local firms to see if they can help for a reasonable price. They may have an intern or junior who can take your project on to keep the cost down. A partner would always be supvising so there should be little risk to such an approach. 

terrapinx

Thanks, I really appreciate the thoughtful answers.

I guess I was hoping there'd be something in-between the DIY forum "just bung in some cellotex" and getting a full set of drawings but it makes it makes sense that doing it right would require calculations and taking every existing element into account. I'll make enquiries, if I aim to get it done before next winter I'll have more time to save up.

FreeBear

Depends on how much of the work you intend to do yourself. For the most part, it is indeed a case of "bung some Celotex in". But you need to pay attention to the detailing (plugging gaps, etc) to avoid draughts and cold spots. The choice of materials and target thicknesses will depend on the space available and the u-value targets set by Building Control (always better to surpass the targets where possible).

Bendy_House

Terra, would you be up for lining the insides of the walls and ceilings at all? Only on the external walls, of course. If you could cope with this level of redecoration-disruption - it would be like having these walls reskimmed, that level of hassle - then this would give you simple and guaranteed results. It would also mean losing ~2" of internal space.

But, if access to the other side of these walls and roof space is difficult and/or there's a risk of blocking ventilating air flow if you go there, then it's a good solution.

Also, fully draught-proof your floor, especially around the perimeter under the skirtings - that's where most of the draughts tend to come from.

terrapinx

Bendy_House Yes! That's the sort of thing I was looking into and would be fine doing myself.

These are the parts I was unsure about:

• The plasterboard on the vertical external (cavity) walls is already mounted on 8cm deep wooden studs - should I put insulation between those? Take the studs down? Leave them but put insulation backed plasterboard over the top?
• The eaves do already have insulation in places, is that a problem if I'm moving to insulate inside the room instead?
  
• Behind the sloping parts of the ceilings (where they're up against the roof) there's already some fibreglass that I'm worried might be blocking airflow, if I closed up more of the other draughts from the room.

And I was worrying the small questions were piling up enough that maybe I needed expert advice.

Mistral001

An architect could help you decide what to do.  It seems to me that you have two options.  First option is to take off plasterboard and existing fibre glass insulation and install insulation board and vapour barrier making sure that the ventilated air gap is maintained.  This might lower the ceiling slightly if  thick insulation board is installed.  Note the vapour barrier will prevent ventilation air from getting into the rooms. This ventilation gap is there to prevent the timbers from rotting and has nothing to do with the ventilation of the house.  Second option is to leave the plasterbaord in place and put on another layer of insulation with plasterboard below this. This will lower the ceilings significantly though and is probably not feasable unless the ceilings are unusually high at present.   The exact specification and how much each option would affect insulation u values etc. any architect or architectural technician should be able to do. 

Bendy_House

Terra, I am sitting in an attached garage which I converted into a habitable room. As it was only 8' wide, I added as little insulation to the single block wall as I could - it was 1" of Jablite (expanded polystyrene insulation, cheap and low quality stuff) which I fitted in between the 2x1 battens I screwed to this wall, and then over-boarded that with the thinnest insulated plasterboard which was only 35mm total thickness.

It is the cosiest and easiest room in my house to heat. A lot of that is down to it being a solid floor (again, a 2" layer of Jablite with T&G floorboards on top) so therefore draught-free.

My point is, whatever you add will/should make a huge difference, and the more you add will make progressively less additional difference. So if your headroom was limited and you only wanted to fit 35mm TLB - which has just 1" of high quality insulation on it - then you can be confident that this will, still, have a very significant effect.

Obviously, more thickness would be better, but if 2" is making things tight, then you can avoid it in most cases.

This is the easiest way to do this job - less work, less destruction, less cost.

However, obviously it would be 'better' if you worked with what you already have. For instance, if you could fit - tightly - 2" of Celotex-type insulation in between these 80mm-deep studs, and press this - tightly - against the back of your existing p'boards, then that would/should do the same thing, and you wouldn't have had to reskim and stuff.

terrapinx

Thanks so much Bendy and Mistral. It's all sounding more do-able again. I think I'll try to fit insulation between the existing studs on the vertical walls (from talking to neighbours it sounds like they probably had polystyrene there at one point), but then board over the sloping roof sections internally so I don't mess with air-flow there. Really appreciate the advice.