MVHR - How to keep upstairs Bedrooms cooler than downstairs rooms?

[JohnW]

Hi

I've been reading a lot of very informative posts in the forum relating to UFH & MVHR and think it is the way I will go with our new build.

 

However...one thing I am struggling with is that we like our bedrooms to be a few degrees cooler than our living spaces, e.g. 21 in Kitchen/Living/Dining and 18 in upstairs bedrooms.

 

Am I right in thinking that if we only have heat on downstairs, the MVHR will distribute some of that heat upstairs? If this is the case, in a well insulated, airtight house surely the temperature upstairs will eventually be the same as downstairs?

 

Appreciate any advice, especially from anyone who has been living with MVHR.

 

Thanks

 

 

 

 

[ragg987]

We have UFH downstairs and basement with whole-house MVHR. House to PH standards.

 

In winter, upstairs remains approx 3-4 C cooler than downstairs. In summer the difference remains - I suspect this is because we generate more heat downstairs from cooking, TV etc and also have large west-facing glazing areas in the kitchen and lounge.

 

MVHR does not re-distribute the heat (e.g. in winter our incoming air is 17-18C vs outgoing air of 20C - these are after the heat-exchanger has done its bit). I have added a 1kW in-line electric heater to upstairs MVHR which we used briefly last winter to for the coldest period.

[jack]

Same with us - bedrooms are cooler most of the year by a degree or two.

 

That said, upstairs is often a degree or so warmer in really hot weather.

[dogman]

If you get a MVHR with a true summer bypass then no heat is recovered so the temperature that is brought in will be the outside temperature, often cooler overnight.

 

Some MVHR's have an electronic bypass that throttle back the fans instead.

[Ferdinand]

Build an upside down house :-), though that may be approaching the issue from the wrong end.

Edited July 5, 2017 by Ferdinand

[ToughButterCup]

Hi, yes, you are correct. the temperature will be even through most of the house.

We went to visit the delightful chap that opens his house every year at Denby Dale. Very informative. He openly admits to having his window open a touch every night. Indeed when we were there, he had both his bedroom window and another window open a bit. Go and visit him. He is very entertaining.

 

@JSHarris (and others) will point to the fact that doing so unbalances the system. And of course they are right. The owner's argument was: so what? Make the system work for you, not the reverse.

I am putting in the infrastructure for the MVHR, this year (ducting), but not the box (Genvex). We'll wait and see what the house can do on its own. We have planned for many of our windows to be openable so we can create natural airflow (chimney effect), but we don't know what the reality of living in our new home will be.

We plan  to record a series of parameters (temperature, RH, CO2 and others - not sure how many yet) for a year or so, and then on the basis of that evidence and the PHPP exercise(s) we ran,  specify the box to be installed in 2018.

 

Don't let MVHR rule you. Yes, we might have to wear a pullover or two for one winter, or go and buy £40 of oil filled heater from Aldi in November.

 

That's a small price to pay for evidence-based expenditure.

[Guest Alphonsox]

We have UFH downstairs and currently nothing upstairs and seem to end up with 2-3 degrees difference (although this section is not fully occupied yet). As a fallback I have wired for electric panel heaters upstairs if we need a top up in darkest winter. 

[Jeremy Harris]

3 hours ago, recoveringacademic said:

@JSHarris (and others) will point to the fact that doing so unbalances the system. And of course they are right. The owner's argument was: so what? Make the system work for you, not the reverse.

 

 

 Just to be absolutely, transparently, clear, I have never, ever, not once, suggested that anyone should keep all their windows closed if they have MVHR!

 

 Yes, opening windows will unbalance the system, so just turn the damned thing off when you do this, to save wasting energy..............

[Stones]

Have to say I've never understood while people get so hung up about opening a window when MVHR is fitted. Houses are for living in and should be as comfortable as possible for the occupant(s).  If that means opening a window now and then, so what.  If that means you waste a few 10's of Watts, so what. Life really is too short to become a slave to your house (at least any more of a slave than you have to be to pay for the damn thing).

[NSS]

We have a Panasonic air rad upstairs running off our ASHP and it can provide cooling to the bedroom in summer or additional heating in winter (UFH downstairs only).

[Jeremy Harris]

2 minutes ago, NSS said:

We have a Panasonic air rad upstairs running off our ASHP and it can provide cooling to the bedroom in summer or additional heating in winter (UFH downstairs only).

 

 

That sounds like a neat solution.  Our bedrooms tend to be a degree or two warmer than downstairs in very warm weather, and I'd been thinking of fitting a cheap air-to-air heat pump, high up in the vaulted hall.  The challenge was going to be getting the refrigerant pipes neatly arranged, especially as this couldn't easily be a DIY job (the pipe runs are too long for one of the pre-gassed systems).

 

However, I think I could run a couple of lengths of 15mm pipe to where I need to get to with a bit of effort, and then connect them to the cooling circuit on the ASHP.  I'll have to have a look around at these air rads - presumably they are a bit like an air con unit indoor unit, are they?

[Barney12]

39 minutes ago, NSS said:

We have a Panasonic air rad upstairs running off our ASHP and it can provide cooling to the bedroom in summer or additional heating in winter (UFH downstairs only).

 

This is a solution I keep heading towards.

However the units I've seen online are not what you might describe as "aesthetically pleasing".? They look rather like large night storage heaters from the 70's.

At the moment I've just allowed for a 4 wire electric rad circuit.

[Jeremy Harris]

I've just been looking around, and the Panasonic units don't seem to look much different from a conventional split air con indoor units, and seem very slim (130mm).  They are pricey for what they are, though.

 

I'll do some more hunting around and see if there are other options.  I've just done a few quick sums and it looks like I could get away with 10mm pipe runs to the sort of size unit we'd need, and running a couple of lengths of 10mm plastic pipe would be easier than running 15mm, I think.

[Roundtuit]

7 hours ago, recoveringacademic said:

 

I am putting in the infrastructure for the MVHR, this year (ducting), but not the box (Genvex). We'll wait and see what the house can do on its own. We have planned for many of our windows to be openable so we can create natural airflow (chimney effect), but we don't know what the reality of living in our new home will be.

 

How does that sit with Building Regs?  Assuming you haven't put trickle vents in windows and don't want uncontrolled airflow through vents, is leaving out the mvhr an option?

[NSS]

This is the type we have http://www.aircon.panasonic.eu/GB_en/product/aquarea-air-radiators/

 

[dogman]

IIrc these rads also need a condensation drain fitting 

I have looked at these before from another manufacturer and have planned to install them upstairs in bedrooms.  

The ones I looked at needed a 22mm flow and return, power,pump control and condensate drain. 

[Jeremy Harris]

22mm seems a bit of an overkill to me. 

 

10mm microbore pipe can deliver 2.5kW at a Δt of around 30 deg C and a flow rate below the noise threshold of around 1.5m/s, so that comes down to about 1kW at a Δt of 12 deg C, which is more than enough - I doubt that we'd need more than around 500 to 600W of cooling up at the top of the house, even in really warm weather.  There would need to be a condensate drain, but that could be small, as I'm guessing these units have the same sort of peristaltic drain pump that air con internal units use, and they use an 8 to 10mm drain pipe.  The existing pump is on it's very lowest setting, so there is plenty of spare capacity available. 

 

 

[NSS]

Ours is 15mm flow and return, and yes there does need to be a condensate drain.

[JohnW]

Thanks for all the replies - seems that the general consensus is that if we do not turn heat on upstairs (not brave enough to have no heating upstairs) the ambient heat from downstairs (via MVHR or rising heat) will be good enough to heat upstairs to 2-3 degrees lower than downstairs which is exactly what we want.

 

 

 

[Bitpipe]

Another MBC house owner here, 4 stories (basement and room in roof) about 400m2. Coming up on 1 year of occupation. Summer has proved more challenging than winter in maintaining a comfortable environment. My tips, repeating some of the above:

• Don't spend the money on heating bedrooms upstairs, you will never use it - especially if you like a cool bedroom (as we do).
• Do have some kind of UFH (electric or wet) in bathrooms to take chill of tiles (due to conductivity, they will feel cooler underfoot).
• Minimise solar gain - consider external blinds / shading etc to reduce overheating.
• Keep windows closed and relevant shutters down during the day in summer, keeps warm air out of the house and prolongs utility of the cool air gained overnight. MVHR in summer bypass keeps air fresh.
• High level opening windows are great for stack ventilation in during summer - this has become our solution and is working well.

We have two large east facing Velux integra (powered and remote controlled) which are closed during the day with blinds down. Once the sun has gone overhead, the blinds go up and the windows open to enable stack ventilation. In the evening we open the west sliders and east windows and get a nice cross draft through the living area. At night, we tilt open the bedroom windows and get a nice cool breeze.

[jack]

Agree with all Bitpipe says.

 

I'll add that I wish we'd thought about insect screens. When it's this hot, it's very pleasant having the windows open once the temp drops in the evening, but being eaten alive by biting insects is less fun. We can also get blowflies stuck inside if we have windows open during the morning or late afternoon at this time of the year.

[Ferdinand]

59 minutes ago, jack said:

Agree with all Bitpipe says.

 

I'll add that I wish we'd thought about insect screens. When it's this hot, it's very pleasant having the windows open once the temp drops in the evening, but being eaten alive by biting insects is less fun. We can also get blowflies stuck inside if we have windows open during the morning or late afternoon at this time of the year.

 

@jackI use mint, having no insect screens or mosquito nets.

 

4-6 sprigs (say 8-12") in a bottle or vase on the sill in rooms which are often most often open to outside. We have one in the conservatory and one in the kitchen. Strip the lower leaves, and these can be used themselves in several ways (look up on tinternet).

 

When the sprigs grow mini roots they are no longer effective, so plant them back into the mint bed to build the stock and get some more. One lot will last 2 weeks or so.

 

It makes a significant difference for us in the number of insects coming in so we have given a whole raised bed over to mint.

 

I am guessing the mechanism is that the aromatic scent will deter insects from entering - which says you may need to try for a few weeks to see the difference. Try it and see.

 

@recoveringacademic can have a mint pot in his winter garden :-).

 

Other plants may also work, but none are so easy to grow.

 

Apparently if you chew a mint leaf before going to bed it helps deter mosquitos, and perhaps your roast-lamb loving beloved will be even more passionate than usual.

 

Ferdinand

 

Edited July 6, 2017 by Ferdinand

[Ferdinand]

We discussed how to keep well insulated houses cooler during the heatwave on a thread last month.

 

I think I have about the best solution for ours until I find a solar film suitable for the outside of our roof windows which will reduce the solar heating significantly. That is without the higher-tech solutions other members have installed.

 

It is create a stack effect by opening a shaded north side window or door on the ground floor (eg in the shaded conservatory), cracking a roof window by 4-6". Then I can direct the (noticeable) current by opening certain doors.

 

One corollary of that is that in future when I renovate houses by adding DG I will make sure that there are least *some* opening toplights and that they have a lockable "ventilation position", so that cross-ventilation can be set up in a secure manner if the Tenants are eg in the back garden or out, or overnight.

 

Ferdinand

Edited July 6, 2017 by Ferdinand

[ToughButterCup]

@Ferdinand, we know when the foxes might well be poking around in our garden: the scent of mint wafts towards our house: if the dogs also bark, we can be certain.  While appreciating the offer, locally mint is abundant, not to say a weed. Now lemon or apple mint, well that would be nice ... I need a good dose of mint now to calm the nerves: Sketchup has frazzled me all damn day. Trying to squeeze quarts into pint pots, while not fully conversant with the software. Arggghhhh.

 

Cross ventilation and opening windows (tilt and turn) it seems to me will be essential. With wafts of mint on the breeze, hopefully.

[ToughButterCup]

BTW lavender works best for mozzies and the like...... a small bowl on each window cill. And geraniums outside the windows if possible.