Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

I also note the fashion for stripped floorboards in houses with
conventional suspended floors with ventilated under-floor spaces. Presto!
under-floor cooling in winter!

So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up? The warm dry air should
discourage damp problems (the reason for the air bricks and thus the cold
air under the floor). Assuming non-tongue-and-grooved floorboards you've
got a ready distribution of warmed air through the floor into the ground
floor rooms. You may have to duct some warm air upstairs and into solid-
floored back extension kitchens and (more importantly) bathrooms in
houses with that layout, and you'd need a source of water heating
(electric or solar). But as a cheap renewable-friendly system, what am I
missing? (Except anyone actually having tried it, natch!)

--
John Stumbles

The ant has made himself illustrious through constant industry industrious
So what? Would you be calm and placid if you were full of formic acid?

On Nov 9, 12:06*am, John Stumbles wrote:

Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

I also note the fashion for stripped floorboards in houses with
conventional suspended floors with ventilated under-floor spaces. Presto!
under-floor cooling in winter!

So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up? The warm dry air should
discourage damp problems (the reason for the air bricks and thus the cold
air under the floor).

2 problems
a) you've got no insulation on the ground, so much of the heat will be
lost. Perhaps you could lay some sort of liquid foam down, I dont
know.
b) You'll have the damp problem from hell. Whether you could deal with
that with the foam layer plus a dehumidifier I dont know.


Assuming non-tongue-and-grooved floorboards you've
got a ready distribution of warmed air through the floor into the ground
floor rooms.

clever

You may have to duct some warm air upstairs and into solid-
floored back extension kitchens and (more importantly) bathrooms in
houses with that layout, and you'd need a source of water heating
(electric or solar). But as a cheap renewable-friendly system, what am I
missing? (Except anyone actually having tried it, natch!)

Warm air into a ceiling void would wipe out the losses due to no
insulation. It would be horribly dusty until all the blowable dust had
been blown out.


NT

On Nov 9, 12:06*am, John Stumbles wrote:
Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

I also note the fashion for stripped floorboards in houses with
conventional suspended floors with ventilated under-floor spaces. Presto!
under-floor cooling in winter!

So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up? The warm dry air should
discourage damp problems (the reason for the air bricks and thus the cold
air under the floor). Assuming non-tongue-and-grooved floorboards you've
got a ready distribution of warmed air through the floor into the ground
floor rooms. You may have to duct some warm air upstairs and into solid-
floored back extension kitchens and (more importantly) bathrooms in
houses with that layout, and you'd need a source of water heating
(electric or solar). But as a cheap renewable-friendly system, what am I
missing? (Except anyone actually having tried it, natch!)

--
John Stumbles

The ant has made himself illustrious through constant industry industrious
So what? Would you be calm and placid if you were full of formic acid?

I don't see how you hope to benefit. Much heat would be lost.
Don't forget, air/air heat pumps become less effective as it gets
colder outside.

"John Stumbles" wrote in message
...
Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

Split units cost about £600 each.
They would be the easiest way to use ASHP for space heating.
Its also the easiest way to get cooling in summer.
You might want one with an additional electric heating element just to boost
it if it is very cold outside or use a fan heater.

On Nov 9, 12:06*am, John Stumbles wrote:

Lack of insulation, as mentioned.

The humidity problem would be one of excessive dryness, rather than
damp. Cold air can only hold a small amount of moisture, even at 100%
Rh. Warming up cold outside air will give supply air at an
unpleasantly low Rh and usually causes problems with contact lenses,
static, thin timber shrinking and cracking, etc..

The other problem would be entrained dirt, causing streaking at any
point where the air enters the living space and dust settling on every
surface. I can't see it working unless the void was accessible and
spotlessly clean, i.e., quite unlike traditional floor voids.

It did work for the Romans, I'm sure it could be made workable.

Ventilation is most effective, IMHO, if supplied filtered at at a
controlled positive pressure. Clean air is supplied and air leaks out
of the building, keeping airborne dust at bay.

In article , harry wrote:
On Nov 9, 12:06*am, John Stumbles wrote:
Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

I also note the fashion for stripped floorboards in houses with
conventional suspended floors with ventilated under-floor spaces. Presto!
under-floor cooling in winter!

So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up? The warm dry air should
discourage damp problems (the reason for the air bricks and thus the cold
air under the floor). Assuming non-tongue-and-grooved floorboards you've
got a ready distribution of warmed air through the floor into the ground
floor rooms. You may have to duct some warm air upstairs and into solid-
floored back extension kitchens and (more importantly) bathrooms in
houses with that layout, and you'd need a source of water heating
(electric or solar). But as a cheap renewable-friendly system, what am I
missing? (Except anyone actually having tried it, natch!)

Underfloor hot air heating has been used, the Roman hypocaust and
related systems. But that was using a floor designed and built for
it, not a retrofit to wooden floors (and using fires, not a heat
pump).


I don't see how you hope to benefit.

By saving the cost of installing proper ducting designed for warm air
heating.


Much heat would be lost.

I suspect to be worthwhile you would have to take up the floors and
insulate the ground and walls of the void, by which time there's not
much void. And if you are doing that work, you could probably install
underfloor heating while you had the floor up....


Don't forget, air/air heat pumps become less effective as it gets
colder outside.

That's equally true of any air source heat pump using outside air.

On 09/11/2011 00:06, John Stumbles wrote:

Something I've been pondering (which falls into the Crazy Idea But It
Might Just Work department)...

Much of the cost of heat pumps systems is getting the heat into the
building. Conventional rads require high temperatures which HPs can't
provide efficiently. UFH is lovely but expensive. Replacing conventional
rads with fan-assisted ones is also pretty expensive.

I also note the fashion for stripped floorboards in houses with
conventional suspended floors with ventilated under-floor spaces. Presto!
under-floor cooling in winter!

So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up? The warm dry air should
discourage damp problems (the reason for the air bricks and thus the cold
air under the floor). Assuming non-tongue-and-grooved floorboards you've
got a ready distribution of warmed air through the floor into the ground
floor rooms. You may have to duct some warm air upstairs and into solid-
floored back extension kitchens and (more importantly) bathrooms in
houses with that layout, and you'd need a source of water heating
(electric or solar). But as a cheap renewable-friendly system, what am I
missing? (Except anyone actually having tried it, natch!)

I suspect to overcome the problems one would need to install some form
of underfloor ducting... Using the void space directly, while
attractive, might have all the practical problems others have listed as
well as that of filling the house with the smell of a musty under floor
void, laced with the fragrance of decaying rat etc. The mustyness may
dissipate with use, but I can't see all the warmth making the space any
less attractive to small critters of all sorts.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
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\================================================= ================/

On Wed, 09 Nov 2011 01:43:06 -0800, Onetap wrote:

Lack of insulation, as mentioned.

Heat loss downwards through the sub-floor:
- standard U value for solid-on-earth floor is 0.36
- temperature of the ground beneath the house is, I think, something like
10C. Let's be pessimistic and say 5C
- suppose heat pump is pushing in air at 30C (you wouldn't want higher)
- then for an 8m * 4m floor (32m^2) you'd lose (32 * 0.36 * (30-5)) = 288W


The humidity problem would be one of excessive dryness, rather than
damp. Cold air can only hold a small amount of moisture, even at 100%
Rh. Warming up cold outside air will give supply air at an unpleasantly
low Rh and usually causes problems with contact lenses, static, thin
timber shrinking and cracking, etc..

One presumably has the same problem with air-to-air heat pumps with the
outlet fixed high on the wall (as illustrated in manufacturers'
literature).

The other problem would be entrained dirt, causing streaking at any
point where the air enters the living space and dust settling on every
surface. I can't see it working unless the void was accessible and
spotlessly clean, i.e., quite unlike traditional floor voids.

Point. But you find a lot of houses with bare stripped boards on the
ground floor; depending on the relative air pressure across the house due
to wind there must be times that one has draughts blowing up through the
cracks, so same problem. And an A-A HP wouldn't generate a howling gale.

--
John Stumbles

I don't know if faith can move mountains
but I've seen what it can do to skyscrapers

On Nov 10, 9:31*am, John Stumbles wrote:
On Wed, 09 Nov 2011 01:43:06 -0800, Onetap wrote:
Lack of insulation, as mentioned.

Heat loss downwards through the sub-floor:
- standard U value for solid-on-earth floor is 0.36
- temperature of the ground beneath the house is, I think, something like
10C. Let's be pessimistic and say 5C
- suppose heat pump is pushing in air at 30C (you wouldn't want higher)
- then for an 8m * 4m floor (32m^2) you'd lose (32 * 0.36 * (30-5)) = 288W

If correct, at 12p/unit thats 3.5p/hr or 83p/day or £200 per 8months
of heating. Per 25yr system life thats £5,000. Factor in a COP of 2
average gives £2,500. So it'd make sense to lift some floor and
insulate, which would also help with damp.

The humidity problem would be one of excessive dryness, rather than
damp. Cold air can only hold a small amount of moisture, even at 100%
Rh. Warming up cold outside air will give supply air at an unpleasantly
low Rh and usually causes problems with contact lenses, static, thin
timber shrinking and cracking, *etc..

Floorboards going from high RH underfloor to dryish would cup badly.
Not disastrous. Joists would crack longitudinally, but again not
disastrous. Cracks would open up between the floorboards.

One presumably has the same problem with air-to-air heat pumps with the
outlet fixed high on the wall (as illustrated in manufacturers'
literature).

* The other problem would be entrained dirt, causing streaking at any
point where the air enters the living space and dust settling on every
surface. I can't see it working unless the void was accessible and
spotlessly clean, i.e., quite unlike traditional floor voids.

Point. But you find a lot of houses with bare stripped boards on the
ground floor; depending on the relative air pressure across the house due
to wind there must be times that one has draughts blowing up through the
cracks, so same problem. And an A-A HP wouldn't generate a

the dust would all be blown out after a while.


NT

John Stumbles wrote:
On Wed, 09 Nov 2011 01:43:06 -0800, Onetap wrote:

Lack of insulation, as mentioned.

Heat loss downwards through the sub-floor:
- standard U value for solid-on-earth floor is 0.36
- temperature of the ground beneath the house is, I think, something like
10C. Let's be pessimistic and say 5C
- suppose heat pump is pushing in air at 30C (you wouldn't want higher)
- then for an 8m * 4m floor (32m^2) you'd lose (32 * 0.36 * (30-5)) = 288W


none of which means a damned thing if the subfloor is vented and full of
a howling -5C gale.


The humidity problem would be one of excessive dryness, rather than
damp. Cold air can only hold a small amount of moisture, even at 100%
Rh. Warming up cold outside air will give supply air at an unpleasantly
low Rh and usually causes problems with contact lenses, static, thin
timber shrinking and cracking, etc..

One presumably has the same problem with air-to-air heat pumps with the
outlet fixed high on the wall (as illustrated in manufacturers'
literature).

The other problem would be entrained dirt, causing streaking at any
point where the air enters the living space and dust settling on every
surface. I can't see it working unless the void was accessible and
spotlessly clean, i.e., quite unlike traditional floor voids.

Point. But you find a lot of houses with bare stripped boards on the
ground floor; depending on the relative air pressure across the house due
to wind there must be times that one has draughts blowing up through the
cracks, so same problem. And an A-A HP wouldn't generate a howling gale.

On Thu, 10 Nov 2011 11:32:54 +0000, The Natural Philosopher wrote:

none of which means a damned thing if the subfloor is vented and full of
a howling -5C gale.

which I why I said in my original post:

"So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up?"

--
John Stumbles

Morality is doing right no matter what you are told
Religion is doing what you are told no matter what is right

John Stumbles wrote:
On Thu, 10 Nov 2011 11:32:54 +0000, The Natural Philosopher wrote:

none of which means a damned thing if the subfloor is vented and full of
a howling -5C gale.

which I why I said in my original post:

"So how about an air-to-air heat pump pushing warm air into the under-
floor void, with the air-bricks sealed up?"

well bad juju in terms of heatloss down through the ground and around
the walls.


putting 45C air on top of cold ground......