Insulation for old house

Oldhousebuild

We are renovating an old 2 story farmhouse. Its constructed of stone walls(approx 2 feet thick, and about 200 years old) and has a pitched roof. Currently there is no insulation of any kind in the house, and it's been stripped down to the bare stone walls.
We are trying to do as much as we can ourselves, on a budget.

I would like to know what thickness of insulation boards would be best to go with? And what would be the best plan (attach direct to plaster, leave space and stud walls etc)

Any advice would be much appreciated as we seem to be going round in circles here!

Thanks!!

TheBoyConor

if you want a good job done on this you really need to know what you are doing. A DIY job is very unlikely to bring about the best results.

External insulation is the better option in many cases but for a farmhouse it might detract from the historic character of the building and might leave damp unaddressed.

Internal dry lining might be a good option. You need to be aware that the wall must be allowed to breath so don't go putting up plastic or sealing things in.
Something like Calsitherm insulation board might be applicable.

For the life of you don't put up extratherm boards as they are not permeable to air and you could end up with all sorts of problems from spalling of external render to dry rot after a few years.

Really to be sure the right decisions are made you should have it assessed by an architect or engineer with an interest in building conservation.

bear in mind that you might qualify for an SEAI insulation grant. If you have a lot of work being done to the house you might qualify for a Deep Retrofit grant.

Also remember that if you are doing a substantial refurbishment to a house you are legally obliged to make the upgrades compliant with the building regs insofar as is reasonably practicable. You can't just decide to just put in a little bit of insulation here and there because "erra, it doesn't suit me".

Partly for this reason, you can't just decide to put up an arbitrary thickness of insulation. You should be aiming as far as possible to get the walls you are insulating down to the current U-value requirements. That will depend on the type of insulation you use, the wall buildup etc. There is more to it than just picking a thickness that suits you.

listermint

All great information. But there is no regulations stopping the op putting whatever insulation thickness they wish in their refurbishment.

Yes getting maximum makes the most sense and should be advocated but there's nothing warranting a minimum spec if they are not doing grant work.

TopTec

In a perfect world BoyConor has it right.

However, in the real world, of budgets and access to decent trades and materials, you can do a good quality job, using basic DIY skills.

I live in a 1800 cottage constructed as yours is. It has taken me 5 years to complete the re-furb. New rooves, (right spelling), 100mm foil backed dry lining, fixed using metal mushrooms, full heatings replacement with stanley range, new tank and standby oil boiler. Full rewire, new floors in most rooms, small sun room extension.

The walls are warm and I have never had damp anywhere. I think the key is to prep the outside as well as the inside. Triple glazing on most windows make the building very efficient.

You need to do your research, boards is a good start but remember you could be talking to a 13 year old who googled his advice!

SEAI is a possibility, but works have to be completed within a tight time frame, 6 months when I did mine so it was of no use.

You can do the ground work for trades like plumbing and electrics, running cables and pipes and getting a qualified trade to finish it and sign it off. Remember you may sell one day and need the certificates to do that or pay for costly inspections.

Everybody has an opinion, just do a search on here for mushroom fittings and read the arguments. Tanking over aqua board is another.

Whatever you choose the DIY way is the cheapest and mostly the best a you will tak care to do the job properly...I coud tell you some stories about crap tradesmen!!!


Hope this helps.
TT

my3cents

Unless there is a really good reason not to I'd 100% go with insulation on the outside. Not really a DIY job though and you do need to go with the thickest insulation possible. The house then becomes a huge thermal mass which when it heats up the heat stays in the walls, provided of course the roof is correctly insulated - floors will also benefit for insulation.

The other option with old farmhouses and we've lived in many is just to keep heat pumped in all the time. We've turned damp unlivable farmhouses into great warm homes with either ranges or stoves running nearly 24/7 but most people aren't around during the day to keep wood burners running and don't have the time or space to cut, stack and dry wood.

If there is damp sealing the house with modern building methods often fails simply because as soon as you do any air movement that was keeping the house dry is stopped and the damp builds up. Ventilation is key.

Some money is also well spent if good surface drains are put in and a land drain around the house to reduce water getting to the foundations. Most farmhouses when built neglected any form of drainage although the old thatched ones often had a box drain running all around the house under the edge of the thatch (in lieu of gutters).

TheBoyConor

As well, if you are replacing floors don't put in concrete floors in an old house. It is not permeable and will force dampness outwards into the walls and you could end up with problems. A breathable slab like a lime based concrete should be considered.

using your regular materials and methods might look fine initially, but problems related to moisture movement through the structure can be going on in the background hidden away and it might be some years before they become apparent.

What I'm saying is just to be careful. You don't want to end up having to tear the place apart again in 10 years because the use of wrong/cheaper every day materials brought about conditions for dry rot or something.

A consultation with a conservation engineer or architect would be a few hundred euros wells spend just so they can guide you in the right direction and stop any terrible ideas before they happen.

listermint

my3cents wrote: »

Unless there is a really good reason not to I'd 100% go with insulation on the outside. Not really a DIY job though and you do need to go with the thickest insulation possible. The house then becomes a huge thermal mass which when it heats up the heat stays in the walls, provided of course the roof is correctly insulated - floors will also benefit for insulation.

The other option with old farmhouses and we've lived in many is just to keep heat pumped in all the time. We've turned damp unlivable farmhouses into great warm homes with either ranges or stoves running nearly 24/7 but most people aren't around during the day to keep wood burners running and don't have the time or space to cut, stack and dry wood.

If there is damp sealing the house with modern building methods often fails simply because as soon as you do any air movement that was keeping the house dry is stopped and the damp builds up. Ventilation is key.

Some money is also well spent if good surface drains are put in and a land drain around the house to reduce water getting to the foundations. Most farmhouses when built neglected any form of drainage although the old thatched ones often had a box drain running all around the house under the edge of the thatch (in lieu of gutters).

My 200 mm of EPS on the outside of my bungalow begs to disagree !



Although i wouldnt recommend to anyone without a stern will and a mindless determination :pac: :pac:

TheBoyConor

That's grand on a typical bungalow. A 200 year old farmhouse is a much more complex scenario for the reasons I outlined above.

Calahonda52

OP:
Hang windows on outside of walls
Fully breathable EWI behind concrete board, with a ventilation space between.
Make house fully airtight.
Leave internal walls as they are or render with lime based render.
Install full MHVR
Job done.
,
No XPS etc or foil backed stuff
no cement based or gypsum based renders
With the MHVR, would be less concerned about the floor: I would dig out, put in a damp proof course, insulate, fit pipes for UFH
When doing the EWI, avail of the work to fit a french drain all the way around the house.
http://www.josephlittlearchitects.com/articles

dathi

listermint wrote: »

All great information. But there is no regulations stopping the op putting whatever insulation thickness they wish in their refurbishment.

.

taken from new partL building regulations 2019 table 7 says you have to comply with among other things table 5 which is the max elemental u values and for solid walls it is 0.35

2.3.2 Where a dwelling undergoes major
renovation, the energy performance of the
whole dwelling should be improved to Cost
Optimal level insofar as this is technically,
functionally and economically feasible.
2.3.3 The cost optimal level to be achieved is:
a) An energy performance of 125
kWh/m2
/yr when calculated in DEAP as
set out in column 2, Table 7
or
b) Implementing the energy
performance improvements as set out in
column 3, Table 7 insofar as they are
technically, functionally and
economically feasible.

antiskeptic

dathi wrote: »

taken from new partL building regulations 2019 table 7 says you have to comply with among other things table 5 which is the max elemental u values and for solid walls it is 0.35

2.3.2 Where a dwelling undergoes major
renovation, the energy performance of the
whole dwelling should be improved to Cost
Optimal level insofar as this is technically,
functionally and economically feasible.
2.3.3 The cost optimal level to be achieved is:
a) An energy performance of 125
kWh/m2
/yr when calculated in DEAP as
set out in column 2, Table 7
or
b) Implementing the energy
performance improvements as set out in
column 3, Table 7 insofar as they are
technically, functionally and
economically feasible.

Who decides whether its 'economically feasible'?
Sounds like a complete get out clause to me.

Have they a definition of 'major' to be guided by?

decky1

A friend of mine has just got his attic [old farmhouse also] sprayed with foam insulation, the guy that did it told him to put 50 mm warmboard on ceiling also , i thought that was a bit much, spoke to a guy that does slabbing and he said no need just ordinary 1/2 inch would do, anyone know any different?

greasepalm

I had the spray foam on roof tiles of old house and in bedroom which had cardboard ceiling i added 30 mm i think it was on ceiling and inside of exterior cold wall.Room is now much warmer,50 is too large.

TheBoyConor

CH, EWI might be an option but I would encourage caution as if it is an old farmhouse EWI would almost completely erase the historic character of the façade. Fine from an energy and thermal pov but it could be a disastrous move architecturally.

GreeBo

Calahonda52 wrote: »

OP:
Hang windows on outside of walls
Fully breathable EWI behind concrete board, with a ventilation space between.
Make house fully airtight.
Leave internal walls as they are or render with lime based render.
Install full MHVR
Job done.
,
No XPS etc or foil backed stuff
no cement based or gypsum based renders
With the MHVR, would be less concerned about the floor: I would dig out, put in a damp proof course, insulate, fit pipes for UFH
When doing the EWI, avail of the work to fit a french drain all the way around the house.
http://www.josephlittlearchitects.com/articles

How do you make it airtight if you are leaving a breathable gap behind the EWI?
Or are you using the concrete board to achieve air tightness?

Calahonda52

GreeBo wrote: »

How do you make it airtight if you are leaving a breathable gap behind the EWI?
Or are you using the concrete board to achieve air tightness?

The breathable wind tightness layer sits in front of the insulation.
The cement board is just a rain shield, good in exposed sites, and is also more robust than the acrylic.
PM me if u want to know where you can see it in a showroom

Wartburg

GreeBo wrote: »

How do you make it airtight if you are leaving a breathable gap behind the EWI?
Or are you using the concrete board to achieve air tightness?

I wouldn´t bother about the air tightness as top priority on the suggested layout. I would be more concerned about the ventilation layer between the external wall insulation and the original walls. This ventilation layer makes the purpose of the external wall insulation useless, because of the thermal looping effect. The external wall insulation has to be treated as non-existend in the u-value calculation. Expensive mistake.

GreeBo

Wartburg wrote: »

I wouldn´t bother about the air tightness as top priority on the suggested layout. I would be more concerned about the ventilation layer between the external wall insulation and the original walls. This ventilation layer makes the purpose of the external wall insulation useless, because of the thermal looping effect. The external wall insulation has to be treated as non-existend in the u-value calculation. Expensive mistake.

Tbh this was what was confusing me...but im now reading it as meaning the EWI can be breathable while also being effectively a draft proof layer, not an airtight layer.