Comfort cooling MVHR

[Jeremy Harris]

15 minutes ago, TFnovice said:

Thanks - I'll do that.

And can I use a gas boiler for heat and an ASHP for cooling on the same UFH system do you know?

 

Not that easily, I suspect, as you'd need a couple of motorised valves, plus you'd have to have both the ASHP and the boiler on the same hydraulic circuit, and I suspect you may well have to put in some form of protection to ensure that under no circumstances could the boiler accidentally feed the ASHP and vice versa.  You might be able to do it using a plate heat exchanger and two separate hydraulic circuits, but TBH it sounds like a lot of expense and complexity,  If you have an ASHP you may we well use it for running the UFH in heating and cooling mode.  Perhaps look at using a DHW only gas boiler?

[scottishjohn]

15 minutes ago, Dreadnaught said:

@TFnovice, just a side note on overheating for well insulated houses. The best mitigant for this is not active ASHP cooling, openable windows, or even shutters but by good house design.

 

Depending on the constraints on your site it may be possible to orient your house, and especially the glazing, and and add shading overhangs and other features that reduce summer overheating dramatically. For example, in the case of Ben Adam Smith of the House Planning Help podcast, his forecast rate of summer overheating by these design measures for his own house was zero percent. In reality, of course, its impossible to fully avoid overheating. However, if your house is also modelled using PHPP then you can see the effect of design changes. Personally, when I chose my architect, was careful to choose one that was familiar with both PHPP and these concepts.

 

Many people who aspire to a (near-ish) passive house don't realise that, with a highly insulated house, space heating becomes easy and it is overheating that becomes the more major concern. Unfortunately, often they discover this only after they take-up occupation.

 

Hope that's helpful.

you can always open the windows,wont, be that many days  when its problem  --or is that too low tech for some.

or do what most australians do,  have overhangs on big windows  +a simple wall mounted air con in bedroom 

[TFnovice]

28 minutes ago, Dreadnaught said:

Hope that's helpful.

 

Yes thanks.  The position of the house is fixed as is the design.  350 days of the year there should be any issues.  Just trying to mitigate the other couple of weeks and the risk of changes in weather patterns affecting us in the future!

[TFnovice]

31 minutes ago, JSHarris said:

Not that easily

 

Thanks for the explanation, but that all sounds much too complicated.  I think I'll look at the air-to-air suggestion and stick with gas UFH and MVHR.

 

12 minutes ago, scottishjohn said:

you can always open the windows ... or is that too low tech for some.

 

Yes but on the days when it's hotter outside than in and there is no breeze, all that does is exacerbate the situation.

[scottishjohn]

2 minutes ago, TFnovice said:

 

Thanks for the explanation, but that all sounds much too complicated.  I think I'll look at the air-to-air suggestion and stick with gas UFH and MVHR.

 

 

Yes but on the days when it's hotter outside than in and there is no breeze, all that does is exacerbate the situation.

then you just have to suck up the running costs of aircon-

how many days a year do you think that will be where you are?

[Ed Davies]

1 hour ago, JSHarris said:

We can heat and cool our slab using a cheap ASHP.  The cooling works far better than I expected and is noticeably more powerful in its effect than the MVHR in cooling mode.  Dead easy to do, as the vast majority of ASHPs have a reversing valve and are quite capable of running in cooling mode, it's just a matter of wiring up a cooling thermostat to set the ASHP into cooling mode and turn on the UFH.

 

With hindsight [¹], would you still bother with A2A heat pump in the MVHR or would you just use the ASHP? A heating/cooling plate in the MVHR supply duct connected to the ASHP circuit?

 

On a house with PV, at the times when the ASHP is needed for cooling running it will be essentially free. Opening windows when the sun's heating the house too much might not be a good idea because of insects, security, etc.

 

[¹] We're going to be sick of “hindsight” puns by this time next year.

[le-cerveau]

1 hour ago, JSHarris said:

Not that easily, I suspect, as you'd need a couple of motorised valves, plus you'd have to have both the ASHP and the boiler on the same hydraulic circuit, and I suspect you may well have to put in some form of protection to ensure that under no circumstances could the boiler accidentally feed the ASHP and vice versa.  You might be able to do it using a plate heat exchanger and two separate hydraulic circuits, but TBH it sounds like a lot of expense and complexity,  If you have an ASHP you may we well use it for running the UFH in heating and cooling mode.  Perhaps look at using a DHW only gas boiler?

 

My ASHP will allow it (though mine isn't wired up for it yet).

 

 

 

Two diagrams form the service manual showing how to do it.

On the first one the 3-way valve is for the ASHP to set Heating/DHW.

Mine is rigged for heating/cooling using 2 x pre-UniQ SunAMp PCM34 units as the Heating buffer and DHW pre-heat.

I am considering as re-plumb/wire as the ASHP has been running for up to 8 hours a day to re-heat the units, It only takes a 2-3 hours if there is no concurrent heating demand otherwise it runs until the heating demand is satisfied (pushing about 34^oC the PCM temperature), then quite quickly climbs to the 44^oC cut off.  The units require 45^oC but stop the call at about 43^oC.

This re-heat is elongated if my mother has a shower (not short) as this also depletes the PCM34 units.

SO I may consider plumbing the boiler heating circuit into the PCM34 units, currently it only supplies the PCM58 units with 65^oC water.

[Jeremy Harris]

4 minutes ago, Ed Davies said:

 

With hindsight [¹], would you still bother with A2A heat pump in the MVHR or would you just use the ASHP? A heating/cooling plate in the MVHR supply duct connected to the ASHP circuit?

 

On a house with PV, at the times when the ASHP is needed for cooling running it will be essentially free. Opening windows when the sun's heating the house too much might not be a good idea because of insects, security, etc.

 

[¹] We're going to be sick of “hindsight” puns by this time next year.

 

I think I'd just use the ASHP, perhaps with a duct cooler as well.  Buying the Genvex MVHR was very much a hasty (and expensive) change of plan, following on from discovering that the temperature in the area we excavated out of the hillside got very hot in summer, when we were doing the ground works.  As the house foundations and frame were all on order by then, I couldn't easily change the design, plus, as you say, opening the windows when it's hotter outside just heats the house up.

 

The running cost for the cooling is always free in practice, as we always have an excess of PV generation whenever we need it.

[TFnovice]

53 minutes ago, scottishjohn said:

then you just have to suck up the running costs of aircon-

how many days a year do you think that will be where you are?

 

I would guess 2 - 4 weeks, so not a nightmare but worth consideration at the design stage.

[scottishjohn]

31 minutes ago, Ed Davies said:

 

With hindsight [¹], would you still bother with A2A heat pump in the MVHR or would you just use the ASHP? A heating/cooling plate in the MVHR supply duct connected to the ASHP circuit?

 

On a house with PV, at the times when the ASHP is needed for cooling running it will be essentially free. Opening windows when the sun's heating the house too much might not be a good idea because of insects, security, etc.

 

[¹] We're going to be sick of “hindsight” puns by this time next year.

insects --yes unthere the midges will be like b52,s.lol

[Stones]

1 hour ago, TFnovice said:

 

Yes thanks.  The position of the house is fixed as is the design.  350 days of the year there should be any issues.  Just trying to mitigate the other couple of weeks and the risk of changes in weather patterns affecting us in the future!

 

I looked very carefully at overheating but after working out the depth and angle of overhang required to eliminate overheating, realised it wasn't something I could easily achieve.  On modelling the house by calculating what the average and maximum daily solar gain would be, I worked out that it was unlikely we would ever exceed 25C inside the house, and so it has proved.  Overheating is of course a relative term, in passive house design, I believe 25C is the generally accepted level beyond which there would be a problem, although I would argue anything over 22 or 23C in summer starts getting uncomfortable.  25C is certainly too hot for me. 

 

As we fitted an ASHP and UFH I have the option of cooling the slab, but as yet have not used it for cooling, primarily because the hot spells don't last long where I live, and I'm prepared (or at least so far) to live with it for a few days.  I looked into fitting a duct heater / cooler but concluded that it wouldn't be able to add anything meaningful in terms of heating or cooling due to flow rates (and limitations on the size/capacity of the heating / cooling duct units).  I've also been in a house that had a Genvex unit fitted, and whilst pleasant standing underneath a supply air vent pumping out cooled air, the flow rates simply were not able to keep pace with the level of solar gain.

 

As you've gleaned from reading the forum, others have a positive experience of using an ASHP to cool the slab, but this would probably be better described as a means of regulating the internal temperature of the house down to a more comfortable level.  A cheap A2A unit, given you are going with gas, may well be the cheapest option of provided a reasonable air cooling capability.

 

 

 

 

[TFnovice]

2 hours ago, Stones said:

I looked very carefully at overheating but after working out the depth and angle of overhang required to eliminate overheating, realised it wasn't something I could easily achieve.

 

Thanks, this is interesting and we are in the same position.  The large overhangs would also not work with the design of our house.  I have looked at louvres, but this creates a problem with cleaning the windows.  I have contemplated continental style external shutters but these leave rooms we would want to use very dark.

 

At the moment I've settled on heat insulating internal blinds.  Whilst these don't stop the heat getting through the glass they do at least stop it heating everything in the room.  So hopefully the solar gain will be minimised.

 

3 hours ago, Stones said:

On modelling the house by calculating what the average and maximum daily solar gain would be, I worked out that it was unlikely we would ever exceed 25C inside the house, and so it has proved.

 

When you say 'modelling' was this done by you or did you get someone else to do this for you?  I presume it was more than just a SAP calc.

 

A cooling element to the MVHR system would only really be to stop it from pulling in warmer air from the outside than the air temp inside and effectively heating the house.  I suppose I could always just turn it off on hot days, but I wasn't sure how happy it would be with being turned on and off regularly and whether this would put it out of balance. To be honest I haven't looked at the extra over cost of one which cools over a standard one (eg the Zehnder or Genflex).  I only know that the 'all singing and dancing' quote I had from THE was a little eye watering and I'd had some surprisingly large quotes for MVHR already.

 

I will have a look at the A2A systems available (I'm getting the hang of the abbreviations) and see whether they are cost effective (ie cheap enough) to warrant installing for the relatively limited use they will get.

[Nick1c]

One of the reasons we are considering Gaulhofer for our windows is that they offer an external blind system, much like a Venetian blind which is retractable, this would be a big help with any unwanted solar gain on our south facing window. Velux also offer external shutters, these can be retro-fitted so I plan to just ensure we can get power to the rooflights in case we need them. 

[Jeremy Harris]

Just now, Nick1c said:

One of the reasons we are considering Gaulhofer for our windows is that they offer an external blind system, much like a Venetian blind which is retractable, this would be a big help with any unwanted solar gain on our south facing window. Velux also offer external shutters, these can be retro-fitted so I plan to just ensure we can get power to the rooflights in case we need them. 

 

Good idea.  If we had been able to fit external blinds (planners wouldn't allow it) then that would have been my first choice.  I stayed in a place in Portugal a few years ago that had concealed metal external roller shutters and they were really great at cutting down solar gain.  I wanted to fit them, or perhaps wooden shutters, but it was made very clear early on in the planning process that there was no way they would have been allowed.

[TFnovice]

5 minutes ago, Nick1c said:

One of the reasons we are considering Gaulhofer for our windows is that they offer an external blind system, much like a Venetian blind which is retractable, this would be a big help with any unwanted solar gain on our south facing window. Velux also offer external shutters, these can be retro-fitted so I plan to just ensure we can get power to the rooflights in case we need them. 

 

This was one of my first thoughts and I have looked at Internorm who offer the same.  But I'm just not sure dark rooms are what I want in summer.

 

Not come across Gaulhofer before. They look interesting - how do they compare price-wise?  And do they cover the whole of the UK.  I see their agent is in Fife.

 

5 minutes ago, JSHarris said:

 it was made very clear early on in the planning process that there was no way they would have been allowed.

 

I'm surprised that is a planning issue - guessing you must be in a conservation area or AONB.

[Alex C]

We have external metal venetian blinds that disappear into the wall above the window when up so they are totally invisible. They are brilliant at stopping solar gain.  I have them so they automatically tilt to track the sun but allow maximum possible view through them.

 

[Adam2]

6 minutes ago, Alex C said:

We have external metal venetian blinds that disappear into the wall above the window when up so they are totally invisible. They are brilliant at stopping solar gain.  I have them so they automatically tilt to track the sun but allow maximum possible view through them.

 

Hi @Alex C would you mind sharing some pics / info on where they came from please?

 

[Jeremy Harris]

10 minutes ago, TFnovice said:

I'm surprised that is a planning issue - guessing you must be in a conservation area or AONB.

 

 

We are inside an AONB and in a CA, plus we're opposite a GII listed building (inside the 100m radius) so had some pretty tough planning restrictions imposed.

[jack]

8 minutes ago, Alex C said:

We have external metal venetian blinds that disappear into the wall above the window when up so they are totally invisible. They are brilliant at stopping solar gain.  I have them so they automatically tilt to track the sun but allow maximum possible view through them.

 

We have the same. Wouldn't be without them, although I don't bother with the solar tracking function.

 

As for light, I don't generally close ours fully. You only need to stop the direct light, which is nearly always achieved with the blinds partly closed. Enough reflected light still gets through to light the room.

 

Nothing keeps the heat out better than external barriers in my opinion. Our bedroom faces east, and unfortunately it's the one place we should have specced blinds but didn't. We have thermal fabric up but it gets hot and radiates into the room. I wouldn't rely on it as a way of keeping a room cool if it gets direct sun.

[Alex C]

They are internorm although the blinds are very similar to the galhoffer ones. Internorm products are great but I really couldn't recommend the  company or the installers. I think the blinds are actually manufactured by another supplier and then just bolted to the windows and colour matched, although when installed they are a really neat design and look an integral part of the window.

[le-cerveau]

10 hours ago, TFnovice said:

This was one of my first thoughts and I have looked at Internorm who offer the same.  But I'm just not sure dark rooms are what I want in summer.

 

We have internorm windows with internal blinds on all windows, the room doesn't have to be dark to keep out the solar gain, you angle the blinds to block the sun but light still gets through, you don't black out the room just tilt the blinds.  They are very effective, so much so that you remember to drop and tilt them to keep out the excessive glare, and consequently solar gain.  You can even program them to do it automatically based on the sun!  I have not yet bothered with this.

[Sue B]

The passivehaus seminar we went to at NSBRC late last year talked about blinds to counteract solar gain.  Their advice was blinds have to be external to be effective.  Even blackout blinds internally let the heat in to the house which then has to be dealt with.  From memory the percentages were 98% effective if outside, 1 or 2 % effective if inside.  I was hoping that they would send the PowerPoint slides but they never arrived.  I will try today to see if they will share as there was info contained in there that would be useful to review at leisure.

[Jeremy Harris]

1 hour ago, Sue B said:

The passivehaus seminar we went to at NSBRC late last year talked about blinds to counteract solar gain.  Their advice was blinds have to be external to be effective.  Even blackout blinds internally let the heat in to the house which then has to be dealt with.  From memory the percentages were 98% effective if outside, 1 or 2 % effective if inside.  I was hoping that they would send the PowerPoint slides but they never arrived.  I will try today to see if they will share as there was info contained in there that would be useful to review at leisure.

 

 

Very true, and the reason that several discussions here have focussed on external methods for preventing solar radiation from getting to the inside pane of the glazing. 

 

However, the Internorm solution uses external blinds that are fitted behind an additional, opening, glass layer on the outside of the sealed unit (or at least the "internal blind" Internorm windows we looked at did).  As such, they are outside the E coated panes, so work pretty much as well as external blinds or shutters.

[Ferdinand]

8 minutes ago, JSHarris said:

the Internorm solution uses external blinds that are fitted behind an additional, opening, glass layer on the outside of the sealed unit (or at least the "internal blind" Internorm windows we looked at did).  As such, they are outside the E coated panes, so work pretty much as well as external blinds or shutters.

 

That sounds ... er ... expensive.

 

Does that mean it is 4 panes of glass? Checking I see that they have at least two versions.

https://www.internorm.com/uk-en/products/sun-protection/

 

(Pity the kid who puts a ball through that).

F

[Jeremy Harris]

28 minutes ago, Ferdinand said:

 

That sounds ... er ... expensive.

 

Does that mean it is 4 panes of glass? Checking I see that they have at least two versions.

https://www.internorm.com/uk-en/products/sun-protection/

 

(Pity the kid who puts a ball through that).

F

 

 

The Internorm windows with internal blinds we were originally going to buy had 4 panes of glass, yes.  The outer pane of glass was separately hinged, so that the blind behind it could be accessed.  I can't recall the model number now, but remember that they were unable to provide the internal blind option for any glazing that needed toughened glass, so the blind option wasn't available for our gable.

 

They weren't cheap, but then it's just cost us £2.5k to fit internal blinds to our gable glazing, plus we spent over £1k on fitting solar reflective film to the outside face of it, so having a solution that addresses both privacy and solar gain within the glazing may not be that different in terms of overall cost.