Conducting heat selectively within a house

[Garald]

Not really an insulation issue, but:

 

I can't be the only person here whose place is substantially warmer on the southern than on the northern side, and particularly so if we are talking about a south-facing room with large windows (call it room A) than about a ground-floor north-facing room (call it room B).

 

Initially, room A was about 3 degrees warmer than room B. Now that I've insulated an outside door properly, the difference is just a bit over 2 degrees. I can work more on thermal bridging and the like, but some difference will still remain.

 

You can see what happens then during the heating season, given that I have a one-zone heat pump: the north side gets to 20C, the heat pump says 'very well, I'll stop working', and room B is now stuck at 18C (or 17.8C, etc) which is too cold for some.

 

In April, this is not a big deal: I just turn off the radiators for all rooms except room B. During winter, however, that is not an option, and fine-tuning everything by hand is bothersome. I've been warned here against getting self-adjusting radiator knobs, as they can interfere with the heat-pump's own self-regulation.

 

What to do? No doubt the simplest coping strategy is "turn off a few radiators or install self-adjusting radiator knobs on just a couple of radiators", but surely there has to be a way to distribute heat from one side of the house to the other side. (That would be useful in summer, too.) It's probably too late in my case, as the renovation is essentially finished, but what do people do - install a heat-conducting conduit indoors, perhaps?

[Super_Paulie]

this is the reason i made my downstairs 2 zone in the end, the north facing room is always significantly colder than my south facing with essentially a full glass wall. So i what i end up with is a room that is 23 on one side and a room that is 18 on the other. Its easily sorted by just leaving the adjoining door open between the rooms and it evens out pretty quickly, but quite often when that door is closed the loop for the north facing room will fire up and circulate and everythings rosy.

Works for me but obviously everyones situation will be different. Ive got rads upstairs and down on TRVs as well but i am yet to use them, seems like wall furniture if nothing else.

[Garald]

4 hours ago, Super_Paulie said:

this is the reason i made my downstairs 2 zone in the end, the north facing room is always significantly colder than my south facing with essentially a full glass wall. So i what i end up with is a room that is 23 on one side and a room that is 18 on the other. Its easily sorted by just leaving the adjoining door open between the rooms and it evens out pretty quickly, but quite often when that door is closed the loop for the north facing room will fire up and circulate and everythings rosy.

Works for me but obviously everyones situation will be different. Ive got rads upstairs and down on TRVs as well but i am yet to use them, seems like wall furniture if nothing else.

 

Right. The problem in this case is that the cold room is the downstairs studio (north-facing), and the only other things I have at ground level are the entrance/laundry and an unheated garage. I don't have an issue on the north side of the first floor, in part because of the heat flow from the warm south-facing rooms and also in part because that floor does get more light (on top of not having a thermal bridge where the foundations end - I'll have to deal with that). Not sure what I am supposed to do. (Drive a metallic spike through the ceiling and into my first-floor shower room? Sounds too adventurous.)

[SteamyTea]

Advection.

This means physically moving a mass about that has different thermal properties.

 

The rest of us know it as blowing warm air about.

[Garald]

15 minutes ago, SteamyTea said:

Advection.

This means physically moving a mass about that has different thermal properties.

 

The rest of us know it as blowing warm air about.

Sounds interesting, though also noisy (the fan that the builder unnecessarily installed in the laundry room certainly is). Of course one can also try to transport heat without transporting a hot substance (air) though I wonder how that would work in this case.

Edited June 3 by Garald

[SteamyTea]

21 minutes ago, Garald said:

Of course one can also try to transport heat without transporting a hot substance (air) though I wonder how that would work in this case.

A thermal diode.

 

You can make your own.

They are basically a pipe, part filled, with a low boiling point fluid.

Stick the bottom part in the hot area, let the fluid change to a vapour, collect the energy at the top of the pipe and transport away.

It is how the element in evacuated tube solar thermal systems work.

[Garald]

1 hour ago, SteamyTea said:

A thermal diode.

 

You can make your own.

They are basically a pipe, part filled, with a low boiling point fluid.

Stick the bottom part in the hot area, let the fluid change to a vapour, collect the energy at the top of the pipe and transport away.

It is how the element in evacuated tube solar thermal systems work.

 

Right, that was an applied friend's guess as to how MVHR worked (but it turns out to be much simpler).

 

 

[JohnMo]

1 hour ago, SteamyTea said:

A thermal diode

Is this really practical on a house scale? I know that's how you can move high temperature in a computer or with solar thermal tubes. But are they practical on a couple degrees difference in room temperature.

 

Would an inter room fan work better?

 

Something like this will do 70m3/h - but very pricey.

 

https://www.ventilationland.co.uk/en_GB/p/brink-indoor-mixfan-co2-controlled--up-to-70-mh/17927/

 

An alternative could be a greenwood CV2GIP, or similar control boost via a couple of temp sensors and switch logic.

 

[SteamyTea]

12 minutes ago, JohnMo said:

Is this really practical on a house scale

Almost certainly not.

Mainly because the phase transition temperature would need to be dynamic.

 

Maybe a ceiling fan in the colder room would shift enough warm air downwards to raise the temperature enough.

[Garald]

> https://www.ventilationland.co.uk/en_GB/p/brink-indoor-mixfan-co2-controlled--up-to-70-mh/17927/

 

Wait, this is being sold as genuine MVHR. If that's what it is, then it's not expensive. Is this for real? What is its efficiency? How does it really work?

 

For context: I am at the end of a renovation at the beginning of which I was poorly advised by someone who had no knowledge of physics and no intuition for it either. As a result, I have PIV (with a pre-heating system which of course doesn't help with efficiency; it's just a strategically placed radiator). The contractor says it's too late to switch it for MVHR, as the ducts for MVHR need to go in every room (I have just one PIV exit per floor) and be larger than the ones for PIV. But if this is not snake oil, it could be a solution to my problem.

[Garald]

Further on unconventional MVHR systems (please tell me if I should make this into a separate thread) - I've just come across this:

 

https://www.vmi-technologies.com/gamme-vmi/double-flux/

 

Not sure how seriously to take it. If this is what I think (a mass of indoor air is exchanged with a mass of outdoor air of the same volume, and then the process recommences) then the efficiency has to be lower than 50%, no? Yet they claim an efficiency of "up to 94%" (of course 0%<94%, so...).

[JohnMo]

29 minutes ago, Garald said:

Wait, this is being sold as genuine MVHR. If that's what it is, then it's not expensive. Is this for real? What is its efficiency? How does it really work?

Read the whole thing including the downloads. It's not MVHR it's part of a cascade MVHR setup. It just an inter room fan? Not MVHR 

[JohnMo]

23 minutes ago, Garald said:

Further on unconventional MVHR systems (please tell me if I should make this into a separate thread) - I've just come across this:

 

https://www.vmi-technologies.com/gamme-vmi/double-flux/

 

Not sure how seriously to take it. If this is what I think (a mass of indoor air is exchanged with a mass of outdoor air of the same volume, and then the process recommences) then the efficiency has to be lower than 50%, no? Yet they claim an efficiency of "up to 94%" (of course 0%<94%, so...).

Similar systems have been about for about decade. They start to cost a small fortune by the time you have everything covered.

[Garald]

1 hour ago, JohnMo said:

Read the whole thing including the downloads. It's not MVHR it's part of a cascade MVHR setup. It just an inter room fan? Not MVHR 

 

Ah. So it's similar to what I posted, and also costs a small fortune?

[JohnMo]

Brink one does. But the alternative I offered - the Greenwood one, is almost silent in operation and cheap to buy. I paid about £40 for one on eBay.

[Garald]

2 minutes ago, JohnMo said:

Brink one does. But the alternative I offered - the Greenwood one, is almost silent in operation and cheap to buy. I paid about £40 for one on eBay.

 

Let me understand - that's not a MVHR system, but rather a moisture-sensitive quiet extract fan without heat recovery?

 

The diagnostics guy recommended something like that. I suppose the idea would be to install that in every room I can, make the envelope airtight (in those rooms) and keep the PIV system (which would now work mainly as an air filter, and to ensure the proper ventilation of every ventilation in which I don't manage to install such a fan)?

[JohnMo]

16 minutes ago, Garald said:

 

Let me understand - that's not a MVHR system, but rather a moisture-sensitive quiet extract fan without heat recovery?

 

The diagnostics guy recommended something like that. I suppose the idea would be to install that in every room I can, make the envelope airtight (in those rooms) and keep the PIV system (which would now work mainly as an air filter, and to ensure the proper ventilation of every ventilation in which I don't manage to install such a fan)?

Sorry your question was about moving heat from one area of the house to another not your ventilation system.

 

@SteamyTea talked about heat pipes, I proposed an inter room fan, which could be ramped up to help even out temperature.  The two types of fan I provided are just fans and nothing really to do with there intended duty. Just being used to move air around the house - not a ventilation strategy, not MVHR or anything else.

[Garald]

Ah, sorry for misunderstanding you. So, what is the role of the Greenwood fan, really? To move air out of wet rooms into the rest of the house?

[SimonD]

13 hours ago, Garald said:

I can't be the only person here whose place is substantially warmer on the southern than on the northern side, and particularly so if we are talking about a south-facing room with large windows (call it room A) than about a ground-floor north-facing room (call it room B).

 

No, you're not. Dealing with this problem I think is where zoning in some way is the necessary approach. Single zone weather compensated installations won't cope well with this because the sensor is on the north wall and there is no further internal feedback loop requesting more or less heat to the space, or a particular part of the space. I personally think this is where one or several internal thermostats could be used that provide combine load/weather compensation and also adjust heat distribution.

 

Your simplest option is to add thermostatic radiator valves to the warm rooms, or add zone valves that are thermostatically controlled. However, following one installation I recently accidentally found that using self-balancing lockshield valves can adjust the heat output of individual radiators in this way, but I haven't done enough testing to know how reliable this is during a heating season.

 

I have to question why you would look at adding technology to solve a problem with another technology's design and installation when you could simply modify it to work properly in a pretty efficient way to begin with. Look at your heating system first.

Edited June 3 by SimonD

[JohnMo]

10 minutes ago, Garald said:

To move air out of wet rooms into the rest of the house

No to move warm air from your warm rooms to the cold ones isn't that what you asked? But as @SimonD says 

 

5 minutes ago, SimonD said:

simplest option is to add thermostatic radiator valves to the warm rooms

 

[Garald]

> simplest option is to add thermostatic radiator valves to the warm rooms

 

Right - but, as I said, some here have told me (and it makes some sense) that it interferes with the heat-pump's regulation of its own flow temperature, and so I am confused.

[Kelvin]

Keep all the doors open. 

[JohnMo]

8 hours ago, Garald said:

> simplest option is to add thermostatic radiator valves to the warm rooms

 

Right - but, as I said, some here have told me (and it makes some sense) that it interferes with the heat-pump's regulation of its own flow temperature, and so I am confused.

This is what my boiler manual said about weather compensation and how to set up the house and it's heating system. Note: system is operated as a single zone, the thermostat valves should modulate individual room radiators instead of switching on/off as a zone valve would do. So the heat pump just sees a small change in return temperature and then modulates it's output as required.

[Garald]

What would seem intuitive to me would be to have the thermostat in the coldest room in the house, *not* install a thermostatic valve there, and install thermostatic valves in all other radiators.

 

Of course this is complicated a bit by the fact that I don't use the coldest room of the house much of the time (it's a guest room; I may find another use for it, but haven't yet). When it's not occupied, it's fine (I think) if on winter days it stays at 17.5C while the other rooms are at 20C. The logical thing to do then may be:

 

- not to install thermostatic valves in either the coldest room or in a room in what is the second coldest space in winter (the attic - the roof insulation is basically that installed 10 years ago),

- if the guest room is being used, set its radiator and that in the room in the attic to max, and let the other rooms regulate themselves; put the thermostat in the guest room; turn down the heating in the attic room if the temperature gets too high or if it isn't being used;

- if the guest room is not being used, set its radiator to a low level (not zero), set the radiator in the attic room to max, put the thermostat in the attic room, and let the other rooms regulate themselves.

 

I suppose the "interference" between the heat pump and the thermostatic valves comes from the fact that, if the thermostat is placed in a room where the radiator has a thermostatic radiator valve, the radiator valve may (and will) close when the temperature is attained, and then the heat pump will not regulate by lowering flow temperature, and we of course want the heat pump to lower flow temperature.

 

Thoughts?

 

(Any recommendations as to thermostatic valves? Also, can their target temperature be set arbitrarily?)

Edited June 4 by Garald

[JohnMo]

You may actually be better heating the whole house and not leaving rooms cold. They will just be sucking heat from the rest of the house, requiring other room to have more heat added to compensate, require a higher flow temp to compensate and lower the CoP.

 

We have a summer house connected to our heating system and it gets used in the mornings throughout the year, I was using a setback temperature (afternoon and night), but ended up using more energy as the heat pump ran flat out trying to heat up after the setback period. Ended setting at the same temperature all the time electric consumption dropped.

 

The less complicated it is, usually the better it is.