Midgo

Me neither but it doesn't make it any less interesting to talk about it
So take below as a discussion, not an argument

Steel will rust in concrete when cracks open, which will eventually happen

You can easily get good anchorage to the composite formed with fibre and cement, like 'big hat' fasteners for FRP perhaps they use something similar

I think the light weight of fibre would be a great advantage both in terms of getting it up there and in terms of loads on the finished thing


And, you're right, there must be very good reasons why they use it

liveaboard

The weight wouldn't be significant compared to the concrete. And the strength of it would do a lot to prevent cracking. The cost would also be pretty small compared to the cost of this work.
Well, you can probably tell from my avatar that I like steel...

Anyway, the proof [as always] is in the pudding. Someone must have done it, and the fiber has obviously become the standard method, so I have to assume there's a reason.

Midgo

Good point - but the weight might be important when you are trying to hold it up whilst you put in the concrete, and it would surely be more drapeable

cost must come into it - it always does, usually at the fore

yes, I had gathered that about avatar, username and steel
I am into FRP, but my avatar was taken aboard a wooden Thames Barge

Pilou

Yes, we are aware of this problem. We plan to use it only when necessary and we will open all windows 20 minutes per day. Hopefully this helps to evacuate the damp.
In the bedroom we use electrical heaters if temp is lower than 15°C.

Pilou

We would prefer a wood burner in the garage coppled with a central heating on the 1st and 2nd floor. But the house has no chimney and I'm afraid it will cost a fortune to make a chimney up to the top of our house.

Midgo

The builders are asking us how thick we want the 'Capoto' external cladding insulation to be for our quote

MrBife has said above, ' 40mm is a good minimum thickness but more is better.'

But I have a few Q's:

• What is the system used here? EPS (expanded polystyrene)? or other foams?
• What thickness's are available?
• Roughly how much in % does an increase of, say for example, 10 mm increase the price? or how thick can you go before it gets silly money?

Cheers

Edit: Just found this that has the below table. Seems like having the thickest isnt a huge % increase in €. Does that sound right?
But what about keeping sufficient overhangs on window sills and roof etc? (I have read 40 mm min for overhangs)

Tabela de Preços: Indicativos

Sistema de Capoto sem EPS (só rede e massa): 20,95 €/m2

Sistema de Capoto com Placa de EPS 3 cm: 28,95 €/m2

Sistema de Capoto com Placa de EPS 4 cm: 29,95 €/m2

Sistema de Capoto com Placa de EPS 5 cm:33,95 €/m2

Sistema de Capoto com Placa de EPS 6 cm: 35,95 €/m2


PPS: This seems to be a helpful site for those deciding between interior and external insulation in the future
http://www.superhomes.org.uk/resourc...-a-solid-wall/

liveaboard

They use dupont wallmate high density expanded polyurethane sheets.
Thicker can cause practical complexities at the windows + doors, etc.

As I believe you to be a practical person, you should calculate your heat loss in watts per M2 at different thicknesses, given the prevailing winter temperatures in + outside. Figure out how much that heat costs you per year, and compare it to the cost of the insulation.
That will give you some real numbers to work with.

Midgo

Thanks,

practical complexities are probably the thing to keep my eye on most of all, to make sure forward thinking has been engaged

Q = U.A.deltaT

Q = heat flow
U = thermal transmittance
A = Area
deltaT = temp diff
t = thickness

U is proportional to t so so is Q and, e.g. 40 mm will have 3/2 heat loss of 60 mm
I know the wall area, roughly, and could look up U values

The trouble is,

• How much of heat goes through walls and how much through roof?
• How much is actual U difference? (its not just foam its foam + other layers + existing walls)
• What about windows, and even if I know their U's how much of A is windows?
• Heat losses through floor?
• How much are heating costs per kWh for a pellet burner & air-con hybrid?
• How to know the integrated values of temp diff, and times heating is used over year?
• I'm lazy

Well, the builders have since said that others in the area have used 60 mm, I think that is the upper limit, but will see how it comes out.
If the quote is too high then we will rethink

If its OK then we will go with that, even if it is over-engineered and my PT wife will be in her sauna house and I will be in my shed in the cold parts of winter

liveaboard

Ignore the doors and windows as you calculate the walls, they have to be calculated separately.
for the sake of simplicity, assume walls 20C and ceiling 25C inside, 10C outside temperature for 5 months.

The burner manufacturer will have an efficiency number; multiply that by the energy content of a kilo of pellets, then subtract 20% to account for error [aka, stinking lies].



find the cost of a kilo of pellets, and multiply by your personal idea of future energy inflation; any number is equally likely to br true.
Do the same for your reverse cycle heat source, but subtract 30% for stinking lies.

Assume brick has zero insulation value; you aren't adding any of that so you don't need to account for the cost or the value in your estimates.

There will be loss around windows, doors, foundation, and roof with a retrofit job like this, there's not much you can do about that.

A tip regarding windows; good double glazed opening ones are expensive, and rarely [if ever] get opened.
large double glazing sections are far cheaper. I took out the old leaky windows and in half of them just put simple thin wooded frames in the holes, to hold the new glass. Big, pleasant, cheap[er].
The other windows are expensive double hinged rubber sealed opening ones.
I had them made to order at a nearby workshop.