Attic Insulation in 17c Listed Building

[Jailhouse John]

I alluded on a previous thread to a major problem I am about to face . The lovely house I am about to shell out my hard earned for has the following problem which I am finding impossible to solve.

Consider this:

The house does not have central heating

It does have 3 huge attic rooms under 60 degree (approx) pitched pantile roofs - unfortunately the pantiles are laid over sarking felt.

There is no natural ventilation via the pantiles because of the sarking.

The roof timbers are all original and generally in great condition however rafters and purlins are all rough hewn, of different sizes and arranged in a variety of ways. So cold bridging will be a nightmare.

The attic floors are all Lime-ash, so presumably laid on reed in the part of the world where the house is located. The underside of the ceiling joists is either more reed and plaster or lathe and plaster. So the floor might have a decent u value in itself.

Inconjunction to installing central heating I am looking to insulate the attics using Kingspan - but how? These rooms are each in the region of 30 feet plus x 15 feet so it will be big bucks if it is technically possible to do at all.

So far I have come up with cutting slots in the sarking near the ridge to open up some ventilation to the space that will be created. Build up rafters with more timber so that they are at least level with each other and then fit 1 layer Kingspan inside rafters/built up timbers plus 1 layer over cross laid. Vapour barrier over that and then plasterboard over all of that.

Building Inspectors will have to be involved and there may well be problems with the CO although I am assued that 'they work together'.

Only other alternative I have come up with is to b***** the attics and insulate under the 1st floor ceilings.

 

[grays85]

similar problem..
our architect advised us to overboard the rafters adding insulation and membrane. leaving an air gap of 50mm vented from the eaves and then fitting new ridge vents. and just have the purlin on show.
We think we may get away with a little less gap on the vent in between the rafters having had a chat with the building regs guy.. and as such we may be able to plaster board (*insulated) between our rafters too. and adding a layer of insulation as we are adding double glazing..iron windows and oak and we are updrading the heating system.. there wasnt one before.. it seems everything has a trade off??

 

[biffvernon]

Do you intend to use the attic rooms?

If not the cheap and easy solution (and which does not interfere with historic fabric) is to lay glass wool insulation over the lime ash floor. You could still provide storage space with suitably balanced planks over the insulation.

Is your house included in my list of lime ash floored properties at http://www.biffvernon.freeserve.co.uk/lime_ash_floors.htm?

 

[Jailhouse John]

Do you intend to use the attic rooms?

If not the cheap and easy solution (and which does not interfere with historic fabric) is to lay glass wool insulation over the lime ash floor. You could still provide storage space with suitably balanced planks over the insulation.

Is your house included in my list of lime ash floored properties at http://www.biffvernon.freeserve.co.uk/lime_ash_floors.htm?

Biff

What a lovely website that is and the lime stuff was excellent information. The house we are hoping to get is not on your website but it is located not a million miles away from you twixt Newark and Grantham so if the deal goes through I will gladly allow you to add its details.

As to my attic problems - well ideally we would have liked to use the them for my study, additional bedroom, small library and storage etc. It appears however that it might have to be filed under 'nice but expensive and complicated' so the simple solution you have proposed or the under 1st floor ceiling method would be prefered. Do you have any idea as to the U value of a Limeash floor?

 

[Nemesis]

As to U values - as this is a listed building, not all modern building regs and requirements apply.

So why worry overmuch?

 

[Jailhouse John]

As to U values - as this is a listed building, not all modern building regs and requirements apply.

So why worry overmuch?

I was trying to get a feel of what thickness of mineral wool on top of the lime ash or Kingspan under the lathe and plaster would be appropriate.

Additionally would there then be a condensation problem on the surface of the limeash. I am told that water and a laid limeash floor are not good bedfellows.

 

[biffvernon]

Why worry? Maybe it's nice to be warm without the guilt of wasting the planet. At least laying insulation over the floor is a reversible job. Later on, when you get the time, money and inclination, you can do a better job of making the sloping roof better insulated. There is, for example, a material made of aerogel called Spacetherm that is an extremely good insulation board - better thermal resistance than PUR or PIR foam of wool products like thermafleece. It's useful where you don't want to lose headroom. But it is expensive.

I don't suppose anybody has measured the U-value of lime ash floors but I would guess its thermal resistance must be similar to plaster, i.e. not very good.

That part of the East Midlands seems to have more lime ash than many parts of the country. There's a very informative SPAB leaflet on the subject.

 

[Nemesis]

I wasn't suggesting no insulation, merely pointing out that calculatiing u values for lime ash may be a bit of a complex job, and that building regs don't have to be adhered to slavishly for a listed building.

 

[biffvernon]

Additionally would there then be a condensation problem on the surface of the limeash. I am told that water and a laid limeash floor are not good bedfellows.

No - but use glass wool that does not come wrapped in plastic. Any water vapour that passes up through the lime ash will then be able to keep going and not condense. Or use wool as in Thermafleece. More expensive but better for the economics of Cumbrian Herdwick sheep. Lovely stuff.

 

[Nemesis]

Can buy Herdwick jumpers too... which could be useful!

 

[Jailhouse John]

The sheep farmers up the road from where I am now would all be driving new 4x4's if I were to lay Thermofleece on the size of these attic floors!!!

 

[Nemesis]

Do what I do - wear thick woolies!

 

[biffvernon]

Here's an alternative that might suit:

http://www.naturalinsulation.co.uk/

 

[Nemesis]

We need to add heaps more insulation before another winter - any idea how prices compare with wool, Biff?

(I have to admit though I am saving hard for Thermafleece, for all manner of reasons!!!)

 

[Jailhouse John]

Has anybody done a cost/benefit analysis on all of these products?

 

[Nemesis]

Well, depends on the view you have of benefit, and what you wish to achieve with the product.

 

[Jailhouse John]

Well, depends on the view you have of benefit, and what you wish to achieve with the product.

Well I am no 'Techy' nor am I an out and out tree hugger but something simple like:

Product Thermal Efficiancy divided by £/sq. m might have been a decent enough start I would have thought.

 

[Nemesis]

Well if you put it that way then there's possibly cheap and nasty to be had.

We tree huggers look at things like Thermafleece as saving an endangered species as well as the planet.

 

[Jailhouse John]

Well if you put it that way then there's possibly cheap and nasty to be had.

We tree huggers look at things like Thermafleece as saving an endangered species as well as the planet.

Well wrt endangered species the hill farmers themselves are more endangered than the Herdwicks are nor do I do 'cheap and nasty' :wink: but being a Yorkshire farmers son I was taught from the cradle to take care of the pennies and the pounds will take care of themselves.

From what I can see you can respect the environment AND ones personal economy as well

 

[Nemesis]

The hill farmers were who I meant, although the herdwicks are in need of a cuddle also.

It's good stuff though.