Pantry keeping it cool with mains water pipe underfloor

[passivhybrid]

Building a passive house at the moment and we have put a pantry on the northside configured to be part of the external envelope to leep it unheated. The plant room is located directly above it meanng  will also have to insulate the pantry ceiling to keep it unheated

 

Have been toying with the idea of running the mains water pipe in a coil on top of the passive concrete slab when final finish floor is being put in. Do you think this will work? Ran this idea by a guy who installs refridgeration units into shops and he suggested running copper pipes and using refridgerant/ coolant , i got lost in the detail but i think he recommended hooking it up to a pump and a sensor it would only  need to be on for a small amount of time

 

has anybody done anything similar?

[Jeremy Harris]

Easy to work out.  Incoming mains water will be at around ground temperature, so ~8 deg C.  Just calculate the heat input to the pantry using the pantry surface U values, then work out how much mains water will flow through the pipe for a typical day (roughly 150 litres per person per day) , then use the heat capacity of water to see just how much heat the cold water will extract from the pantry.

 

I don't have time to do the sums now, but if I had to guess, I'd say that the cooling effect would be about the square root of bugger all...

[jamieled]

We have a similar plan in that we have a pantry on the north facing side. Plan is to stick some insulation on top of the slab and have a couple of vents to outside. Wasn't keen on anything more sophisticated.

[Jeremy Harris]

16 minutes ago, jamieled said:

We have a similar plan in that we have a pantry on the north facing side. Plan is to stick some insulation on top of the slab and have a couple of vents to outside. Wasn't keen on anything more sophisticated.

 

 

I think this has been discussed here before, but I can't find the thread.  Any pantry built like this needs a well insulated door, and all walls that face into the thermal envelope, ceiling, floor, etc need to be well-insulated and sealed.  If including vents to outside then the pantry door also needs to be airtight, so the easiest solution might be to just use a decent external door as the pantry door, as that will have the required seals and be reasonably good thermally.

 

Another approach might be to just build the house with a "notch" in the external thermal envelope, that runs around where the pantry will go, with an uninsulated external wall over the notch.

 

Whatever approach is used, it's worth remembering that the outside temperature will often be well above the temperature needed for a pantry for a fair part of the year, so the pantry may well end up warmer than the rest of the house at times.

 

If I were going to do this, then I think I'd forget trying to put vents to outside, forget trying to use a thin wall to outside, and just build a well-insulated cupboard wherever I needed it to be, and fit it with a decent door, with an airtight sealing system (probably a suitably redecorated external door).  I'd then just fit a small air-to-air heat pump in it, to keep it at a constant temperature.  Doesn't need to be anything big, the sort of cooler units fitted to small delivery vans would be about the right size, might even be a bit too powerful.  Failing that, a small monoblock ASHP, supplying chilled water to a cold shelf in the cupboard would probably do the job.

 

Still cheaper and easier to just buy a larder fridge though...

 

 

[jamieled]

@JSHarris I think I remember the thread as well. That's pretty much what we've done with the exception of the heat pump. Got a joiner to build an airtight door and the envelope is the same as the rest of the house (but keeps the larder separated from the rest of the house if you get my drift). The vents can be closed if necessary.

In all likelihood this is not really replacing a fridge, more just a big store cupboard. If I had free will I'd probably not have bothered, but I was overruled at the design stage!

[passivhybrid]

42 minutes ago, jamieled said:

@JSHarris I think I remember the thread as well. That's pretty much what we've done with the exception of the heat pump. Got a joiner to build an airtight door and the envelope is the same as the rest of the house (but keeps the larder separated from the rest of the house if you get my drift). The vents can be closed if necessary.

In all likelihood this is not really replacing a fridge, more just a big store cupboard. If I had free will I'd probably not have bothered, but I was overruled at the design stage!

We visited my uncles newly built passive house a few years ago before w started our build., his only gripe was that the house was so well insulated that he couldnt keep his fruit or vegtables from detoriating rapidly and he had resorted to storing his veg outside in his shed this was what cemented  the idea of a pantry for us. 

[Onoff]

6 hours ago, passivhybrid said:

his only gripe was that the house was so well insulated that he couldnt keep his fruit or vegtables from detoriating rapidly

 

That just sounds like sour grapes to me...

[Nickfromwales]

How do those cheapo wine ‘coolers’ work? Maybe a pair of those minus the doors / bastardised ? Prob is, to get ‘cold, the byproduct is heat  Remote systems seem the obvious choice.

 

I’ve got the same conundrum with a job where they are building on a plot, in a vineyard where they produce champagnes, and want a large wine store in the middle of their PH  . Looks like a split A/C unit running at its lowest setting may fit the bill but really have to look at condensation risks, and the quality of the glazing units in the sliding glass wall designed to be a viewing aid. Main issue is that it’ll reside within the general heated and airtight envelope, so a few more nights of pencil chewing before I offer my first thoughts. 

“What could possibly go wrong?” ?

[Russell griffiths]

6 minutes ago, Nickfromwales said:

How do those cheapo wine ‘coolers’ work? Maybe a pair of those minus the doors / bastardised ? Prob is, to get ‘cold, the byproduct is heat  Remote systems seem the obvious choice.

 

I’ve got the same conundrum with a job where they are building on a plot, in a vineyard where they produce champagnes, and want a large wine store in the middle of their PH  . Looks like a split A/C unit running at its lowest setting may fit the bill but really have to look at condensation risks, and the quality of the glazing units in the sliding glass wall designed to be a viewing aid. Main issue is that it’ll reside within the general heated and airtight envelope, so a few more nights of pencil chewing before I offer my first thoughts. 

“What could possibly go wrong?” ?

Nick I have worked in a couple of houses that had cool rooms with glass walls and doors, big enough to get 20-30 people inside, luxury houses £5 million type places, so you must be able to get the kit. 

[Conor]

Planning a fully insulated and airtight room in the basement using ICF to form a pantry. Will have its own external air vent. Will also have provision for a future air con unit (just like @JSHarris Recently I stalled in his bedroom) for £500-£700 if it turns out to be too warm in the summer. Price wise, a bit more than a large fridge but the storage are will be huge.

 

I don't think you'd ever get enough water flow though to have a effective cooling effect. And depending on your water source, temperature of mains water can be in the mid teens in the summer. Ours was 18c this summer. You'd have virtually no cooling effect. You'll also have heat transfer through your floor structure to adjacent spaces.

 

And I'd also be against it for a couple more reasons. As your water is going through more pipework than required, you'll have a slight pressure drop. Also, you might be tempted to leave a tap running for a few minutes for a better cooling effect now and again... A criminal waste of water.

[vivienz]

I believe that exactly this set up was done by @Weebles.  They may be able to offer some advice on how it has worked out for them.

[Russell griffiths]

When this was discussed in the other thread I think the thoughts where any pipe work on show would condensate leaving a drippy pipe making a mess. 

[ProDave]

50 minutes ago, Nickfromwales said:

How do those cheapo wine ‘coolers’ work? Maybe a pair of those minus the doors / bastardised ? Prob is, to get ‘cold, the byproduct is heat  Remote systems seem the obvious choice.

 

This sounds like a job for one of those "kit" fridges that you build into boats.

[Cpd]

I remember the other thread just.... I have a lean to on the back of my house (north side) with a back door going into it  from the kitchen. In there I have my wooden veggie boxed and other storage cupboards. Works fine but could definitely be improved upon. I really like the idea of and outside / inside larder as in the future I want to preserve my own veg on a larger scale. When I was a kid we had a storage shed for our home grown produce, made of thick stone and heavy tile roof. It was located in a cold dark corner of the garden under the shade of a big old tree. My parents stored all manner of fruit and vegetables in there that they had grown for many months after the growing season had finished. 

[Nickfromwales]

35 minutes ago, ProDave said:

This sounds like a job for one of those "kit" fridges that you build into boats.

Still have to get rid of the ‘waste’ heat though? 

[ProDave]

8 minutes ago, Nickfromwales said:

Still have to get rid of the ‘waste’ heat though? 

Because they come as a kit with pipes that have to be connected (like @JSHarris little aircon unit) you can put the evaporator outside under a suitable cover.

[joe90]

In a previous house plan I had a larder outside the thermal envelope and had a mad idea of including a large ladder fridge in it but moving the compressor through the wall into the kitchen so it heated the kitchen not the larder. Never got round to it but I thought the theory was good ??

[Onoff]

Wasn't it just a big slab of marble in the old days?

[joe90]

3 minutes ago, Onoff said:

Wasn't it just a big slab of marble in the old days?

 

Yes, but in a cold draughty old house, not a passive house?

[Onoff]

2 minutes ago, joe90 said:

 

Yes, but in a cold draughty old house, not a passive house?

 

Terrific, I just need the marble slab then!

[Jeremy Harris]

46 minutes ago, Onoff said:

Wasn't it just a big slab of marble in the old days?

 

Either a slab of marble or, in the house I grew up in, a concrete shelf in the larder covered with white tiles (the whole inside of the larder was done in white tiles). There was an external vent grill down near floor level and another near the ceiling, to allow air to circulate.  The kitchen (and larder) were on the North side of the house (had been part of the servant's quarters at our old house, complete with separate staircase and indicator bell system in the kitchen). 

 

The operating principle was to ensure that the larder had a high heat capacity (hence the "cold" shelf) and to prevent it getting any solar gain at all.  That way it would end up at around the mean daily temperature, cooling slightly during the night and warming slightly during the day, with the high heat capacity of the shelf and tiles helping to maintain an even temperature.

 

However, a look at the mean daily temperature data shows that a passive larder like this would never have stayed very cool in summer.  This is the mean daily temperature for our area (data from the Met Office), for example:

 

 

This shows that for about 5 months of the year a simple vented larder would be above 10°C, and for a couple of months it would be above 15°C, assuming that it was perfectly insulated from the inside of the house.  In practice the inside of the house will always leak some heat into the larder, so it will be slightly warmer than these mean daily temperature data would suggest, plus it would be a source of heat loss from the house.

 

The myth that larders were always cool places really goes back to the days before we had refrigerators, where a ventilated space like this would always be cooler than the house, so better for keeping perishables in.  The reality is that they weren't ever very effective, and anyone that really wanted to keep food fresh (and had the money to do so) would have an ice house, usually built underground, or in a basement.

 

A larder built into a basement, and insulated well from the thermal envelope of the house would stay at the typical UK ground temperature, which is about 8°C.  Not as cool as a fridge (they are typically around 3°C to 4°C) but fine for storing fruit and veg, cheese and possibly wine.

[Ed Davies]

Something which could be tried to help keep a larder cool would be a thermosyphon to an external radiator higher up. That would act as a thermal diode so that heat went out but not in so that the larder would tend to track the average daily lows, rather than the average daily averages, IYSWIM. If the external radiator was facing the sky and protected from radiation from the surroundings it'd tend to track the night-time sky temperatures as well.

 

I'm thinking of two radiators connected bottom-left in, top-right out (or whatever) in a loop full of water/glycol with just a little pressure vessel to deal with expansion/contraction. No pump or controls.

[passivhybrid]

7 hours ago, Ed Davies said:

Something which could be tried to help keep a larder cool would be a thermosyphon to an external radiator higher up. That would act as a thermal diode so that heat went out but not in so that the larder would tend to track the average daily lows, rather than the average daily averages, IYSWIM. If the external radiator was facing the sky and protected from radiation from the surroundings it'd tend to track the night-time sky temperatures as well.

 

I'm thinking of two radiators connected bottom-left in, top-right out (or whatever) in a loop full of water/glycol with just a little pressure vessel to deal with expansion/contraction. No pump or controls.

 

The external radiator part would be difficult in practice

[Ed Davies]

2 hours ago, passivhybrid said:

The external radiator part would be difficult in practice

 

In what way?

[passivhybrid]

maybe i misunderstood it........ by external radiator do you mean placing it outside the building?