I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.
At some point in the last few decades, it's been plasterboarded 50mm
over the stone, but not insulated.
Attic insulation has been put in, to a depth of 100mm, then boarded
over.


An average of some 3Kw departs through the walls over the year.

With rising energy prices, this is a bad thing.

So.
I've bought 50mm kingspan - for going round the windows, and 100mm
rockwool, for going up the walls, plasterboard to go over all of this.

Some tests I did with the rockwool indicate it's fine for this - can be
hung fairly staightforwardly from a bit of timber folded over some at
the top, and doesn't show any signs of tearing.

Behind the rockwool, will be a 1-2cm gap from the stone, and then
landscaping fabric - porous polypropylene sacking type material, stapled
to the existing wood. (I happen to have a large roll)

At the base of the wall, this looks like:



W FRRRP
W FRRRP
W FRRRPS
W KKP|S
W KKP|S
W KKP|S

R = rockwool P = plasterboard, K = kingspan, S = skirting board,
F=fabric, W = wall |= 2mm steel (that I also have enough lying around
of.)

The cavity behind the plasterboard contains metal conduit for network/
power/foo.

Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

To keep the insulation nice and dry.
I know the proper solution is airbricks, but basically, that's not going
to happen, it's a nightmare (50cm stone walls)

The fans turn on once a day at midday for half an hour or so (or
possibly when something detects that the humidity is the lowest it's
been in 24 hours, I'm unsure)

The skirting board/plasterboard/metal sandwitch can be unscrewed easily
in sections, to allow for easy access to electrics/network cables.

I'd hope for the insulation to hit 0.4W/m^2/K, for a total over 110m^2
of walls of maybe 400W at 10C difference - compared to the current 3Kw
or so.

I'm expanding the existing 50mm wood against the stone not with solid
wood, but with 15mm wood the same width as the existing, but installed
on frequent 35mm blocks glued+screwed to the original wood, with kingspan
in the gaps.

This doesn't of course do that much for the insulation - but I have lots
of 15mm thick wood suitable, but no 60, and it helps a fair bit.

Any comments?

I know that this isn't ideal, it's very much a low budget solution. An
expensive one simply can't be done.

And going below 400W isn't really needed - once the windows are fixed,
the total heating needed drops to around a kilowatt or so, most of which
will be doable from solar gain and waste heat.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

On 25 Oct 2006 14:22:01 GMT, Ian Stirling
wrote:

I'd hope for the insulation to hit 0.4W/m^2/K, for a total over 110m^2
of walls of maybe 400W at 10C difference - compared to the current 3Kw
or so.

Have a look at Actis Tri-Iso
http://www.commercialconnections.co.uk/18.html
http://www.roof-solutions.co.uk/ours...894_33485.html
http://www.proctorgroup.com/proctor.asp?left=103

It is meant for roofs but might be useful in your application and has
a uValue of 0.19 W/m2/K. It is also vapour resistant.

--
Peter Parry.
http://www.wpp.ltd.uk/

Peter Parry wrote:
On 25 Oct 2006 14:22:01 GMT, Ian Stirling
wrote:

I'd hope for the insulation to hit 0.4W/m^2/K, for a total over 110m^2
of walls of maybe 400W at 10C difference - compared to the current 3Kw
or so.

Have a look at Actis Tri-Iso
http://www.commercialconnections.co.uk/18.html
http://www.roof-solutions.co.uk/ours...894_33485.html
http://www.proctorgroup.com/proctor.asp?left=103

It is meant for roofs but might be useful in your application and has
a uValue of 0.19 W/m2/K. It is also vapour resistant.

Ok.
Of the two working links - one gives a price.
I find it rather surprising that it doesn't actually say that 189
pounds buys you 10 or 20 square meters.

This is between 9 and 4.5 times more expensive than rockwool - and I
did mention that I'm on a budget...

Neglecting this.

The pages constantly say 'this insulation value can't be measured in
conventional tests', and give testimonials to another test methodology.

At the very least, I want to have actual details of this test
methodology, not just an unattributed statement saying that it
is good.

The product has an R value of 0.6 (without cavity) as mentioned on the other
working link, for a U value of 1.66 - and therefore .055 W/m/K conductance,
assuming it's 33mm thick.

I'd want a damn good reason why this is better than a 33mm thick sheet
of polystyrene, with foil on each side, which comes in at maybe 3 pounds
per square meter, compared to the 19/9 pounds a square meter.

Or even 30mm of rockwool, and foil on each side which may end up at an
even lower price.

On 25 Oct 2006 16:36:43 GMT Ian Stirling wrote :
The pages constantly say 'this insulation value can't be measured in
conventional tests', and give testimonials to another test methodology.

At the very least, I want to have actual details of this test
methodology, not just an unattributed statement saying that it
is good.

http://www.planningportal.gov.uk/upl...n_july2005.pdf

is a a report that suggests that the TRADA tests are not valid.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.

An average of some 3Kw departs through the walls over the year.

With rising energy prices, this is a bad thing.

I know that this isn't ideal, it's very much a low budget solution. An
expensive one simply can't be done.

And going below 400W isn't really needed - once the windows are fixed,
the total heating needed drops to around a kilowatt or so, most of which
will be doable from solar gain and waste heat.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

Cardboard is probably one of the cheapest insulators. It traps air, and
is free in quantity if you walk round any town at bin time. I know
you've got the budget for rockwool, but was just wondering whether some
hybrid solution could get you more result for less money. Since
cardboard is not moisture resistant in any way, that limits how and
where it can go.


NT

wrote:
Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.

An average of some 3Kw departs through the walls over the year.

With rising energy prices, this is a bad thing.

I know that this isn't ideal, it's very much a low budget solution. An
expensive one simply can't be done.

And going below 400W isn't really needed - once the windows are fixed,
the total heating needed drops to around a kilowatt or so, most of which
will be doable from solar gain and waste heat.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

Cardboard is probably one of the cheapest insulators. It traps air, and
is free in quantity if you walk round any town at bin time. I know
you've got the budget for rockwool, but was just wondering whether some
hybrid solution could get you more result for less money. Since
cardboard is not moisture resistant in any way, that limits how and
where it can go.

Well.
There is a slight tradeoff between cost and space.
If it wasn't actually as good as rockwool, I'd need more space.
At the moment, rockwool means that I lose about 6cm - which adds up
to around 3% loss of space.
Cardboard would make this worse AIUI.

If I was _really_ on the pennies - and 700 quid was unaffordable, I'd
still be going with rockwool, but probably 50mm, topped with the
existing plasterboard.

This is only about 150 quid.
Payback would be in a winter.

Or maybe even simply remove bottom 5" of existing plasterboard, seal
properly to wall, and pour in lots of polystyrene bean-bag filling from
holes drilled in the wall, following up with wallpapering with foil,
skimming.
A fair bit less work, but more expensive than the previous solution.

Unless of course I went round skips for polystyrene, and chipped them to
get particles to pour in.

I might be wrong but... Here goes anyway...

Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.

Behind the rockwool, will be a 1-2cm gap from the stone, and then
landscaping fabric - porous polypropylene sacking type material, stapled
to the existing wood. (I happen to have a large roll)

The gap needs to be between the stone and the fabric doesn't it? 1-2cm is
really pushing the limit of what's going to allow adequate ventilation. 30
to 50mm would seem more practical / installable. Rockwool is very moisture
tolerant, especially if supported enough to stop it sagging.

At the base of the wall, this looks like:

W FRRRP
W FRRRP
W FRRRPS
W KKP|S
W KKP|S
W KKP|S

R = rockwool P = plasterboard, K = kingspan, S = skirting board,
F=fabric, W = wall |= 2mm steel (that I also have enough lying around
of.)

The steel worries me. Isn't that going to condense any moisture on to your
plasterboard and skirting? And the kingspan I know is a corrugated steel
pre-insulated sandwhich... Is that what you mean?

Any comments?

Just those above...

fluffkin wrote:
I might be wrong but... Here goes anyway...

Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.

Behind the rockwool, will be a 1-2cm gap from the stone, and then
landscaping fabric - porous polypropylene sacking type material, stapled
to the existing wood. (I happen to have a large roll)

The gap needs to be between the stone and the fabric doesn't it? 1-2cm is
really pushing the limit of what's going to allow adequate ventilation. 30
to 50mm would seem more practical / installable. Rockwool is very moisture
tolerant, especially if supported enough to stop it sagging.

Yes - 1-2cm between the stone and the fabric.

It's marginal - which is why I'm using fans to actually blow
air past it from the floor void. (1/2 hour a day or so)
It's more to keep the wood dry, than the rockwool.
I'm going to stick in a few sensors at the same time, as that's free.

Yes, 50mm would be nice.
But, that's another percent or so off the house volume... (and a number
of more awkward things as I need to move doors)

fluffkin wrote:
I might be wrong but... Here goes anyway...

Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.
snip
At the base of the wall, this looks like:

W FRRRP
W FRRRP
W FRRRPS
W KKP|S
W KKP|S
W KKP|S

R = rockwool P = plasterboard, K = kingspan, S = skirting board,
F=fabric, W = wall |= 2mm steel (that I also have enough lying around
of.)

The steel worries me. Isn't that going to condense any moisture on to your
plasterboard and skirting? And the kingspan I know is a corrugated steel
pre-insulated sandwhich... Is that what you mean?

Oops.

It's actually aluminium, and it's not corrugated, as much as 'as flat as
they can get it.'

No - the steel is to protect the cables from the over-enthusiastic with
drills in the future.

The metal is directly behing the skirting board, on the 'hot' side of
the insulation.

The kingspan is there so that there can be enough space behind the
insulation at the bottom to run cables, and have a void to blow air
through, without compromising on insulation value - as it's twice as
insulating as rockwool.
I'd like to go all the way up with kingspan - as that would make it
a hell of a lot easier - but it'd add 600 quid to the cost.

Ian Stirling wrote:
wrote:
Ian Stirling wrote:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.

An average of some 3Kw departs through the walls over the year.

With rising energy prices, this is a bad thing.

I know that this isn't ideal, it's very much a low budget solution. An
expensive one simply can't be done.

And going below 400W isn't really needed - once the windows are fixed,
the total heating needed drops to around a kilowatt or so, most of which
will be doable from solar gain and waste heat.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

Cardboard is probably one of the cheapest insulators. It traps air, and
is free in quantity if you walk round any town at bin time. I know
you've got the budget for rockwool, but was just wondering whether some
hybrid solution could get you more result for less money. Since
cardboard is not moisture resistant in any way, that limits how and
where it can go.

Well.
There is a slight tradeoff between cost and space.
If it wasn't actually as good as rockwool, I'd need more space.
At the moment, rockwool means that I lose about 6cm - which adds up
to around 3% loss of space.
Cardboard would make this worse AIUI.

Has anyone measured cardboard's insulation value? I assume youre right,
bigger pores and all. It might be handy to know what its value was
though.


If I was _really_ on the pennies - and 700 quid was unaffordable, I'd
still be going with rockwool, but probably 50mm, topped with the
existing plasterboard.

This is only about 150 quid.
Payback would be in a winter.

Or maybe even simply remove bottom 5" of existing plasterboard, seal
properly to wall, and pour in lots of polystyrene bean-bag filling from
holes drilled in the wall, following up with wallpapering with foil,
skimming.
A fair bit less work, but more expensive than the previous solution.

Unless of course I went round skips for polystyrene, and chipped them to
get particles to pour in.

Labour value would be murderous though. One could simply use household
rubbish - plastic, paper, carrier bags, wrapping - nothing nasty. A lot
of people are not doing solid wall insulation because of the cost, this
sort of thing could enable more such insulation on a diy basis.
Assorted cardboard boxes cut down to 2" also work, giving a 2" cavity
with lots of baffles to almost stop air movement.


NT

On 25 Oct 2006 14:22:01 GMT, Ian Stirling
wrote:


Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

To keep the insulation nice and dry.
I know the proper solution is airbricks, but basically, that's not going
to happen, it's a nightmare (50cm stone walls)

The fans turn on once a day at midday for half an hour or so (or
possibly when something detects that the humidity is the lowest it's
been in 24 hours, I'm unsure)


I dont think the fans would work as you hope, wouldn't it need to vent
to outside at the top of the walls? Such a small gap would presumably
put up quite a resistance to air movement aswell. Then how do you get
access to the fans to service them?

marvelus wrote:
On 25 Oct 2006 14:22:01 GMT, Ian Stirling
wrote:


Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

To keep the insulation nice and dry.
I know the proper solution is airbricks, but basically, that's not going
to happen, it's a nightmare (50cm stone walls)

The fans turn on once a day at midday for half an hour or so (or
possibly when something detects that the humidity is the lowest it's
been in 24 hours, I'm unsure)


I dont think the fans would work as you hope, wouldn't it need to vent
to outside at the top of the walls? Such a small gap would presumably
put up quite a resistance to air movement aswell. Then how do you get
access to the fans to service them?

I'd try my very best to do it all with kingspan/celotex/xtratherm etc.
I'm on a budget also but there are dealers on ebay etc. who sell
seconds at lower prices. I also got my local builders merchant to give
me some 50mm 2.4 x 1.2 m sheets delivered for £20 inc. vat.

nafuk wrote:

marvelus wrote:
On 25 Oct 2006 14:22:01 GMT, Ian Stirling
wrote:


Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

To keep the insulation nice and dry.
I know the proper solution is airbricks, but basically, that's not going
to happen, it's a nightmare (50cm stone walls)

The fans turn on once a day at midday for half an hour or so (or
possibly when something detects that the humidity is the lowest it's
been in 24 hours, I'm unsure)

I dont think the fans would work as you hope, wouldn't it need to vent
to outside at the top of the walls? Such a small gap would presumably
put up quite a resistance to air movement aswell. Then how do you get
access to the fans to service them?

Good quality fans - I have had identical ones running for a couple of
years.
And the skirting board just unscrews, and you get to them easily.

I've actually found somewhere the flow resistance of a rectangular box,
and computed it. It's not a problem - the flow rate is _very_ low,
around 1cm/s or under.


I'd try my very best to do it all with kingspan/celotex/xtratherm etc.
I'm on a budget also but there are dealers on ebay etc. who sell
seconds at lower prices. I also got my local builders merchant to give
me some 50mm 2.4 x 1.2 m sheets delivered for ?20 inc. vat.

That's the price I got at Jewsons, more or less.

Unfortunately, another 550 quid or so isn't really possible ATM.
The only advantage this would have is labour saving, and space saving,
not actual energy.

Peter Parry wrote:
On Wed, 25 Oct 2006 21:53:06 +0100, AJH
wrote:

On Wed, 25 Oct 2006 16:38:15 +0100, Peter Parry
wrote:

It is meant for roofs but might be useful in your application and has
a uValue of 0.19 W/m2/K. It is also vapour resistant.

Isn't this the one that the asa upheld a complaint against in may 2006
because their tests did not conform to any standard? This of course
doesn't mean it doesn't work.

No idea, I can't find anything on the ASA web site about it. The
paper Tony mentioned is quoting a Um value of around 0.5 (R-value of
1.71 m2K/W). The only bit I've got is about 6in sq so not much use
for measuring anything :-). The advantage in this application would
be that it would replace both the insulation and vapour barrier and
take up somewhat less space. However, the cost appears to rule it

The vapour barrier in this case takes no space - it's foil PVA'd onto
the back of the plasterboard. (yes, I was too cheap to buy foiled
plasterboard, I find that a pressure sprayer filled with diluted PVA,
and kitchen foil is really fast to apply.)

On 25 Oct 2006 14:22:01 GMT, a particular chimpanzee named Ian
Stirling randomly hit the keyboard and
produced:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.
At some point in the last few decades, it's been plasterboarded 50mm
over the stone, but not insulated.
Attic insulation has been put in, to a depth of 100mm, then boarded
over.

You're probably losing a lot of heat through your roof.

An average of some 3Kw departs through the walls over the year.

I'm not sure what you mean. 3kW is a rate of energy transfer and only
gives you a figure of how much you're losing per second. If you mean
3kWh, then this is a minuscule amount over a year.

A 600mm stone wall has a U-value of about 1.33W/m^2K; in other words,
1.33 Watts for every 1 degree (Kelvin or Celsius) difference between
one side of the wall and the other. Multiply this heat loss by an
average 10 degree difference over the heating season x 18 hours x 180
days (the period the heating is on) x 110m^2 (wall area) / 1000 (W to
kW) gives 4,740kWh of energy lost through the walls per year.

Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

This sounds like a bad idea. You'll be drawing up cold, damp air into
the space between your insulation and your wall. It'll condense on
the inside of your wall and permeate into your Rockwool.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

How much Rockwool could you buy for your loft for that money? 200mm
laid over your ceiling joists would reduce the fabric heat loss from
0.46W/m^2K to 0.13W/m^2K. You could put the rest between your floor
joists.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Hugo Nebula abuse@localhost wrote:
On 25 Oct 2006 14:22:01 GMT, a particular chimpanzee named Ian
Stirling randomly hit the keyboard and
produced:

I have a 1300s or so Scottish farm cottage.
50-60cm stone walls.
At some point in the last few decades, it's been plasterboarded 50mm
over the stone, but not insulated.
Attic insulation has been put in, to a depth of 100mm, then boarded
over.

You're probably losing a lot of heat through your roof.

Well - not really.
There is 100mm of fibreglass in there.

Adding 100mm of fibreglass may be almost as hard as doing the
plasterboard downstairs, with a tiny fraction of the payback.

An average of some 3Kw departs through the walls over the year.

I'm not sure what you mean. 3kW is a rate of energy transfer and only
gives you a figure of how much you're losing per second. If you mean
3kWh, then this is a minuscule amount over a year.

However, I'm talking of an average power over the year.
snip
Also, there are every few meters small fans that draw air from under the
(suspended, ventilated) floor and blow it up the walls.

This sounds like a bad idea. You'll be drawing up cold, damp air into
the space between your insulation and your wall. It'll condense on
the inside of your wall and permeate into your Rockwool.

It's actually fairly warm dry air. (noninsulated suspended floor) if I was to
insulate the floor, then I will need to do something else.

At 700 quid for 110m^2, it's not horribly bad, and should pay back in
under 3 years.

How much Rockwool could you buy for your loft for that money? 200mm
laid over your ceiling joists would reduce the fabric heat loss from
0.46W/m^2K to 0.13W/m^2K. You could put the rest between your floor
joists.

0.46W/m62K * 80 = 36W/K = 360W at 10C difference.
0.13W/m^2K * 80 = 10W/K = 100W at 10C.
So, a saving of 260W, for a hell of a lot of work - the attic is already
boarded, as well as reducing quite a bit of usable space.


And maybe another 700W by doing the floor too. (not to mention the floor
would involve a hell of a lot more expense and work.

Versus around 2600W by doing the walls.

Thanks for the comments.
However, I believe that once I have done the walls, and the next long
pole - replacement sealed units for the single pane windows (700W@10C)
then the house should actually pretty much run on around 1-1.5Kw at
10C difference.
Add a small 2m^2 solar thermal panel on the roof, and I think I can
almost turn the heating off forever.
I may not bother with this - the payoff on this is quite long.

Ian Stirling wrote:

Thanks for the comments.
However, I believe that once I have done the walls, and the next long
pole - replacement sealed units for the single pane windows (700W@10C)
then the house should actually pretty much run on around 1-1.5Kw at
10C difference.
Add a small 2m^2 solar thermal panel on the roof, and I think I can
almost turn the heating off forever.
I may not bother with this - the payoff on this is quite long.

Whats your cost figure for that? Are you using a glass glazed frame
with mylar film secondary layer, and 2 layers of black mesh for
absorber, or something less efficient and more expensive? If you were
able to put it at ground level this would reduce costs more, and you
could do away with the fan. Also you surely want more than 2 m^2, quite
a bit more to see you through as much winter as possible.

I'm beginning to wondering if youre talking about water heating?


NT

wrote:
Ian Stirling wrote:

Thanks for the comments.
However, I believe that once I have done the walls, and the next long
pole - replacement sealed units for the single pane windows (700W@10C)
then the house should actually pretty much run on around 1-1.5Kw at
10C difference.
Add a small 2m^2 solar thermal panel on the roof, and I think I can
almost turn the heating off forever.
I may not bother with this - the payoff on this is quite long.

Whats your cost figure for that? Are you using a glass glazed frame
with mylar film secondary layer, and 2 layers of black mesh for
absorber, or something less efficient and more expensive? If you were
able to put it at ground level this would reduce costs more, and you
could do away with the fan. Also you surely want more than 2 m^2, quite
a bit more to see you through as much winter as possible.

I'm not quite sure.

I suspect it may be as simple as a couple of old radiators, feeding into
the heating loop, underneath a double-glazed insulated cavity in the
roof.
As I have most of the stuff for this, and air heating is rather more
annoying to implement.
(though a means of solar heating intake air is interesting.)

I'm beginning to wondering if youre talking about water heating?

Yes - but not hot water heating.
Rather as the radiators are now 3-4 times oversized, they should output
enough to keep the place warm at 20C over ambient or so.
There may well be an additional warm water store, I'm not sure.

Ian Stirling wrote:
wrote:
Ian Stirling wrote:

Add a small 2m^2 solar thermal panel on the roof, and I think I can
almost turn the heating off forever.
I may not bother with this - the payoff on this is quite long.

Whats your cost figure for that? Are you using a glass glazed frame
with mylar film secondary layer, and 2 layers of black mesh for
absorber, or something less efficient and more expensive? If you were
able to put it at ground level this would reduce costs more, and you
could do away with the fan. Also you surely want more than 2 m^2, quite
a bit more to see you through as much winter as possible.

I'm not quite sure.

I suspect it may be as simple as a couple of old radiators, feeding into
the heating loop, underneath a double-glazed insulated cavity in the
roof.
As I have most of the stuff for this, and air heating is rather more
annoying to implement.
(though a means of solar heating intake air is interesting.)

I'm beginning to wondering if youre talking about water heating?

Yes - but not hot water heating.
Rather as the radiators are now 3-4 times oversized, they should output
enough to keep the place warm at 20C over ambient or so.
There may well be an additional warm water store, I'm not sure.

Hot water to heat the house is going to give you a lot of penalties. No
wonder you didnt judge it worthwhile. There are freezing issues,
plumbing, heat exchanger if using antifreeze, and output temp too low
to be genuinely compatible with existing CH systems... and at the end
of it efficiency of such systems is low anyway.

What would be the sticking point with hot air heating? It'd be way less
work, some common issues are workroundable, and cost and payback are
both much better than hydronic.


NT

wrote:
Ian Stirling wrote:
wrote:
Ian Stirling wrote:

Add a small 2m^2 solar thermal panel on the roof, and I think I can
almost turn the heating off forever.
I may not bother with this - the payoff on this is quite long.
snip
I'm beginning to wondering if youre talking about water heating?

Yes - but not hot water heating.
Rather as the radiators are now 3-4 times oversized, they should output
enough to keep the place warm at 20C over ambient or so.
There may well be an additional warm water store, I'm not sure.

Hot water to heat the house is going to give you a lot of penalties. No
wonder you didnt judge it worthwhile. There are freezing issues,
plumbing, heat exchanger if using antifreeze, and output temp too low
to be genuinely compatible with existing CH systems... and at the end
of it efficiency of such systems is low anyway.

However, as I've got drastically oversized radiators, due to the
upgraded insulation - it's not quite as bad as that.

No, there is no way that it'll hit normal CH temps.
40C in much weather should be quite achievable, and give a pretty good
temperature boost.

Freezing is of course an issue - in my case this is likely to be dealt
with by simply using a frost stat, to heat up the radiator a tad.

What would be the sticking point with hot air heating? It'd be way less
work, some common issues are workroundable, and cost and payback are
both much better than hydronic.

Noise.
Filtering.
Power consumption of fans.
Large ducts through awkward spaces.
Very hard to store heat.
Valves are more awkward.
Insulation of ducts is much, much harder.

If I had a warm roof, then I'd certainly be going for heated air.

Stirling

Ian Stirling wrote:
wrote:

Hot water to heat the house is going to give you a lot of penalties. No
wonder you didnt judge it worthwhile. There are freezing issues,
plumbing, heat exchanger if using antifreeze, and output temp too low
to be genuinely compatible with existing CH systems... and at the end
of it efficiency of such systems is low anyway.

However, as I've got drastically oversized radiators, due to the
upgraded insulation - it's not quite as bad as that.

yes, but each time your CH comes on it knocks the solar gain out.
Unless you've got a system where you can set the circulating water temp
to modulate to the minimum needed to achieve the right heating temp at
any time.

OTOH DG panels should perform better with CH, which is really whats
wanted for year round use.


No, there is no way that it'll hit normal CH temps.
40C in much weather should be quite achievable, and give a pretty good
temperature boost.

Freezing is of course an issue - in my case this is likely to be dealt
with by simply using a frost stat, to heat up the radiator a tad.

Right. One more complication though. Not sure how the pump plus frost
heater power consumption compares to the optional low speed fan for hot
air.


What would be the sticking point with hot air heating? It'd be way less
work, some common issues are workroundable, and cost and payback are
both much better than hydronic.

Noise.
Filtering.
Power consumption of fans.
Large ducts through awkward spaces.
Very hard to store heat.
Valves are more awkward.
Insulation of ducts is much, much harder.

If I had a warm roof, then I'd certainly be going for heated air.

There are silent low speed fans, though not many are designed for that.
Noise is most easily dealt with by using a passive system, no fan at
all. Power consumption is then zero.

The easiest & highest % ROI way to address ducts is to have none, and
only heat 1 side of the house directly. The other side gets partial
heat from the temp difference mentioned below. You then have no ducting
insulation either. This works if your CH can cope with the differing
heat output requirement, ie has some form of room stats.

Heat storage, again its easier not to for maximum ROI %. If you want
the place heated in the day this works fine. There is some evening heat
storage in practice, because you can set the solar stat to above the CH
stat. IOW your solar heats the house to the upper end of what you
decide is comfortable, and after sundown this temp slowly falls for a
while until CH needs to come on. This avoids the evening warm up plus
some ongoing heating.

If by valves you mean to prevent night time cooling, a plastic film
damper closes when theres no panel airflow in the desired directoin.
This thin damper will lose a bit of heat at night, but the daytime gain
well outweighs that.

If you mean for automatic thermostatic control, a servo plus light
hinged rigid damper will work. polystyrene would approx eliminate the
small night time heat loss. Yes its a bit harder than switching a pump
off, but much easier than the complications of a hydronic system.

The ducting details above assume your panels are at ground & maybe
first floor level. If they're on the roof, a single duct down the
corner of a room would suffice for some types of layout. Air returns
upward through the living spaces, with a grille & wrapped duct for the
attic. Only the attic duct needs any insulation.

For a fanned roof mouted system, a noise filtering labyrinth at the top
can make the system virtually silent. DG panels support much higher
working output temp, which works with less air flow. Having used a
labyrinth for a job here I've been impressed with them, very effective.

If you want to avoid a periodic clean, vehicle air filters are cheap
and readily available.

Systems that heat less than all the house all the time are always open
to extension in future if desired. Flat panels perform ok in overcast
conditions, and can be located away from the house if need be. Mesh
absorbers give very good efficiency figures.

Not sure how much of issues this addresses.


NT