Extractor fan operated by an hourly timer?

[riveralt]

One point you do need to remember from the Gruadian article is that

'It is also important that the door is insulated: a good way to do this would be to adhere a sheet of 50mm-thick polystyrene to the pantry side of the door (this can be clad with moisture-resistant MDF and decorated). Remember to ensure good draught-proofing around the door.'

The second point is that this article dates back to 2007 - you will need to check that the Building Regulations have not changed.

Finally, just out of interest, in view of the implied suggestion that you are just building a very inefficient fridge, what do you intend to store in this location?

 

[travisbickle]

One point you do need to remember from the Gruadian article is that

'It is also important that the door is insulated: a good way to do this would be to adhere a sheet of 50mm-thick polystyrene to the pantry side of the door (this can be clad with moisture-resistant MDF and decorated). Remember to ensure good draught-proofing around the door.'

The second point is that this article dates back to 2007 - you will need to check that the Building Regulations have not changed.

Finally, just out of interest, in view of the implied suggestion that you are just building a very inefficient fridge, what do you intend to store in this location?

Potatoes, onions, flour, rice, condiments, spices, store cupboard items. Basically everything which wouldn't ordinarily be stored in a fridge.

 

[JohnW2]

You'd really have to ask an expert about that. Given that warmer air rises, I could see the logic in the opposite of that.

That's my concern.

Without being an expert, I have to say that my inclination would probably be to extract at the top. I'd be interested to hear what other people think.

While I have your attention John, lack of insulation under the concrete floor slab - will that have a significant impact on ambient temperature? There is a consideration to perhaps build the room lower into the ground.

Again from a non-expert perspective, I frankly doubt it would make much difference. You could always put insulation over the floor if you wanted to. I doubt that going down (presumably only a modest distance) lower would make much difference. Historically, of course, the floor (if not also the walls) would probably have been kept wet - a crude sort of AC, relying on the heat extraction when the water evaporated!

However, don't forget my earlier comments that, in summer, the whole concept is a bit iffy. Your only real hope would be that cooling achieved during the night would (given adequate insulation and lots of 'thermal masses' within the pantry) persist during the day. You'd certainly probably want to switch off the fan (either manually or with a thermostat) during the day, since the outside air temperature would probably be above the desired temperature of your pantry, so the last thing you'd want to do would be to circulate that outside air through the pantry during the day.

What sort of temperature are you ideally hoping to achieve in your pantry?
Edit: I've just seen your last post. With the exception of potatoes and onions (and anything similar), none of the things you mention really need to be stored below ambient temperature, do they?

Kind Regards, John

 

[travisbickle]

10 - 18 degrees or so.

 

[JohnW2]

10 - 18 degrees or so.

In the absence of some active cooling (i.e. AC) (or wet floors/walls!), you obviously won't be able to achieve a temperature lower than that of the outside air (maybe just at night, in summer). In recent weeks in the UK, that would have put you towards the top of that range, even at night (and I doubt that it would have persisted that low during the days).

Kind Regards, John

 

[stillp]

I don't think you need any form of active cooling. All you need is large thermal mass, 'cold' surfaces such as stone or concrete, and good natural ventilation. My attached garage is on the north side of the house, and is well ventilated by the gaps around the up-and-over door, and is always significantly cooler than the house.
I certainly wouldn't wet the floor, which will cool the floor slightly but also warm the air as well as increasing the humidity.

 

[stillp]

Ignore - double post

 

[JohnW2]

I don't think you need any form of active cooling. All you need is large thermal mass, 'cold' surfaces such as stone or concrete, and good natural ventilation. My attached garage is on the north side of the house, and is well ventilated by the gaps around the up-and-over door, and is always significantly cooler than the house.

As I said, if the only 'cooling system' is ventilation with outside air, it's physically impossible that air temperature within the pantry could be lower than that of the outside air - which, even at night, would have been in mid-teens (°C) recently. If one only allowed that air circulation to happen at night, if the pantry (particularly door) was well insulated and if, as we've both said, there was lots of thermal mass in the pantry, then the daytime temperature in pantry might not rise too much above the night-time outside air temperature - but it obvioulsy would rise a bit, and certainly could never be below that night-time outside air temp.

I certainly wouldn't wet the floor, which will cool the floor slightly but also warm the air as well as increasing the humidity.

I hope that you, and others, understood that my 'historical aside' (complete with exclamation marks) comment related to what the Victorians might well have done, not a suggestion for the present-day! Apart from anything else, the whole thing would probably become mouldy very quickly!

I would also add that the inside of my garage is currently appreciably cooler than the 'outside air' - but that would presumably not be the case if outside air was deliberately being circulated through it.

Kind Regards, John

 

[stillp]

if the only 'cooling system' is ventilation with outside air, it's physically impossible that air temperature within the pantry could be lower than that of the outside air

No it isn't. I understand why you're saying that but it isn't that simple. You have to consider the rate of heat input, the rate of heat output, and the thermal storage capacity of the room, as well as the specific heat of the materials.
16 - 18 deg C is not likely to be achievable in ambient temperatures in the high 20s though.
Forced ventilation will actually make the room warmer unless the energy used to drive the fan can be dissipated somewhere else.

 

[EFLImpudence]

Potatoes, onions, flour, rice, condiments, spices, store cupboard items.

So, all the things which don't need to be kept cold or even particularly cool.
They seem to survive very well in my kitchen units.

Keeping them dry is more important - perhaps a dehumidifier could be built in as well to counteract all the moist air being drawn in.

Basically everything which wouldn't ordinarily be stored in a fridge.

Why is that, do you think?


Well, I'm going to say it -

whilst it is your house and you may obviously do as you wish, this is a ridiculous project.

 

[JohnW2]

...if the only 'cooling system' is ventilation with outside air, it's physically impossible that air temperature within the pantry could be lower than that of the outside air

No it isn't. I understand why you're saying that but it isn't that simple. You have to consider the rate of heat input, the rate of heat output, and the thermal storage capacity of the room, as well as the specific heat of the materials.

I realise I'm seriously simplifying, but I'm not sure I understand what you're saying - so maybe I haven't been clear enough.

No matter what the heat input into the room (from adjacent rooms and through any outside walls), and no matter what the thermal storage capacity/specific heat of what is inside of the room, then if (as I assume will be the case) the 'coldest' thing introduced into the room is the outside air (during the period it was 'let in', which during summer would be just at night) (and assuming no phase changes, such as with the Victorian's wet floor ), then there surely is no way that the contents of the room can ever fall to below the temperature of that outside air (at the time it was allowed in). For that to happen would require the transfer of heat from a cooler to a hotter body/material/whatever - which is contrary to the laws of physics.

Obviously, as I've said, if one had plenty of thermal capacity in the pantry and good insulation, and circulated outside air through the pantry only at night, then the panty temperature could be well below the daytime outside air temperature (being a partial persistence of the situation which had existed during the night) - but what it could not be is below the lowest temperature the outside air had been when it was 'allowed in' (during the night).

Doi you still disagree?

Forced ventilation will actually make the room warmer unless the energy used to drive the fan can be dissipated somewhere else.

I suspect that will be a fairly trivial effect, but it would obviously only literally make the room warmer if it raised the temperature of the outside air it was pumping into the room to above the temperature of the room - which would be a situation that thermostats would presumably be adjusted so as to avoid.

Kind Regards, John

 

[stillp]

No, I don't disagree with what you've said now, but that wasn't what you said earlier, when you were wrong.

Obviously the effect of the energy dissipated by the fan will have an effect that depends on where it is dissipated, but I would assume it would either be in the incoming air stream or in the room itself.

 

[JohnW2]

No, I don't disagree with what you've said now, but that wasn't what you said earlier, when you were wrong.

Fair enough - but. with respect, I would still think that, in context, it ought to have been fairly clear what I meant, even if the actually words I wrote, if taken alone and at face value, were not correct. As I'm sure you understand, the point I had been trying the make to the OP was that, if the only 'cooling' was that resulting from passing outside air through the pantry, in recent days/weeks that would have meant that (even if that outside air circulation was stopped during the day), the pantry temperature during the daytime could not possibly have been below 'mid-teens', quite possibly greater, since it was bound to be a bit above the the lowest temp of the previous night's outside air.

Obviously the effect of the energy dissipated by the fan will have an effect that depends on where it is dissipated, but I would assume it would either be in the incoming air stream or in the room itself.

I would imagine that the great majority of the (small amount of) heat generated by the fan (assuming that's what you're talking about) would be transferred into the airstream, wouldn't it?

Kind Regards, John

 

[stillp]

No, I don't disagree with what you've said now, but that wasn't what you said earlier, when you were wrong.

Fair enough - but. with respect, I would still think that, in context, it ought to have been fairly clear what I meant, even if the actually words I wrote, if taken alone and at face value, were not correct. As I'm sure you understand, the point I had been trying the make to the OP was that, if the only 'cooling' was that resulting from passing outside air through the pantry, in recent days/weeks that would have meant that (even if that outside air circulation was stopped during the day), the pantry temperature during the daytime could not possibly have been below 'mid-teens', quite possibly greater, since it was bound to be a bit above the the lowest temp of the previous night's outside air.

Obviously the effect of the energy dissipated by the fan will have an effect that depends on where it is dissipated, but I would assume it would either be in the incoming air stream or in the room itself.

I would imagine that the great majority of the (small amount of) heat generated by the fan (assuming that's what you're talking about) would be transferred into the airstream, wouldn't it?

Kind Regards, John

Oh, I'm sorry. I thought we were meant to read the words you wrote, rather than guess what you would have written if you'd thought more about it.

The heat transfer into the airstream will only be a part of the heat dissipation of the fan. The radiated heat and the convected heat as the fan cools down will affect the room temperature if the fan motor is inside the room, which I would expect it to be. Pretty marginal I agree, but it will make a difference.

Leaving all that aside, people have been storing stuff in cold larders for centuries without the use of electric fans, so I agree with EFLI this is a pretty silly idea.

 

[JohnW2]

Oh, I'm sorry. I thought we were meant to read the words you wrote, rather than guess what you would have written if you'd thought more about it.

The real problem is that I don't have a good enough crystal ball to tell me which bits of my writing people are going to quote, and then criticise, in isolation I agree that the part of one of my sentences which you quoted was 'incorrect'. However, if one were to read (or quote) the entire paragraph, then I think my meaning was probably fairly clear to most readers. Whatever, if I didn't express myself clearly enough, I apologise. I've now spelt out precisely what I meant, and we seem to have no disagreement about that!

Leaving all that aside, people have been storing stuff in cold larders for centuries without the use of electric fans, so I agree with EFLI this is a pretty silly idea.

I'm inclined to agree, particular given what the OP has told us about intended usage. As you will have seen, my first significant posting in this thread started...

I think there are probably some potential flaws in the whole idea.

.. and then before EFLI joined in, I added:

Edit: I've just seen your last post. With the exception of potatoes and onions (and anything similar), none of the things you mention really need to be stored below ambient temperature, do they?

Having said that .... for years before they acquired a fridge, my grandparents had an 'outside 'pantry' (part of the house structure, next to the 'outside loo'), just outside the kitchen door, on the north side of the house, full of marble shelves. It had large, meshed-covered openings at top and bottom which, during the summer, were manually 'closed' (with heavy shutters) during the day and opened at night (during winter, they were just left open all the time) - which I suppose was, in some senses, the mid-20th century equivalent of a thermostatically-controlled electric fan!

Kind Regards, John.