Charging using 32amp Commando and mobile charger

[Avendit]

Just some detail about our house.

Technically we only have a passive haus extension; because it was very very hard to upgrade the "old part". Having done that we were so impressed with the MVHR we decided to retro fit it to the old part (which, luckily, was already very air tight).

The old part had been upgraded from original - double glazing, cavity fill, loads of insulation in loft, insulation around all the window reveals and so on

What we had done was to swap a hugely inefficient building, with massive air leakage allowing pletny of fresh air / air changes, and loads of heating - which probably, back-in-the-day, took care of moulds etc. - for an air tight, minimal air change, well insulated, minimum heating, building. Loads of condensation on windows in the morning, and mould spores for sure (even if no actual mushrooms growing on the ceiling!)

We installed MVHR in the old bit and that completely solved the condensation and improve the air quality hugely - much as you described after yours was repaired. We are really really pleased with that - but we wouldn't have done it but for our positive experience of MVHR in the new part. Blooming nightmare to accommodate retrofit MVHR as the air pipes are large diameter, so may not be possible/easily in other houses.

Thus I concur with your experience that MVHR helps with condensation / air quality.

But ... the building has to be made very air tight for it to work

Loving our MVHR retrofit too, but it's not all sunshine.

• It's a hard retrofit (and installers will to take it on are few and far between - one father/son combo in Scotland).
• The passivhaus rated unit we chose, silencers and ducting is taking up half of our attic. We couldn't fit it to our extension with kitchen and utility as pipe routing just wasn't possible. All open plan tho so kind of included, but still using external venting cooker hood etc.
• Routing even the pipes we do have was frankly hell. Needed to co-install with a new bathroom as we needed 4x 12cm pipes layed through there to get downstairs. All integrated and neat now, but an uphill battle to persuade the rest of the family it was going to work.
• In summer we aren't getting the full bennifit as we still have all the windows down. But that is mostly an overheating problem we have and are addressing separately.

On the bright side, you do get bennifits at lower air tightness than SAP calcs would have you believe, I've seen some papers proposing fixes in next version of sap.

Other benefits as noted by others re air quality really noticeable. Bathrooms are dryer, washing drys quicker, much fresher air, especially overnight.

I love it, but accept the case isn't as clear as the solar.

 

[RedMod3]

Just some detail about our house.

Technically we only have a passive haus extension; because it was very very hard to upgrade the "old part". Having done that we were so impressed with the MVHR we decided to retro fit it to the old part (which, luckily, was already very air tight).

The old part had been upgraded from original - double glazing, cavity fill, loads of insulation in loft, insulation around all the window reveals and so on

What we had done was to swap a hugely inefficient building, with massive air leakage allowing pletny of fresh air / air changes, and loads of heating - which probably, back-in-the-day, took care of moulds etc. - for an air tight, minimal air change, well insulated, minimum heating, building. Loads of condensation on windows in the morning, and mould spores for sure (even if no actual mushrooms growing on the ceiling!)

We installed MVHR in the old bit and that completely solved the condensation and improve the air quality hugely - much as you described after yours was repaired. We are really really pleased with that - but we wouldn't have done it but for our positive experience of MVHR in the new part. Blooming nightmare to accommodate retrofit MVHR as the air pipes are large diameter, so may not be possible/easily in other houses.

Thus I concur with your experience that MVHR helps with condensation / air quality.

But ... the building has to be made very air tight for it to work

Yes, our bungalow was built in 1989 and when we eventually replaced our MVHR system with a better one, it wasn’t too hard. We used steel pipes rather than corrugated aluminium in the new system and we remove the heat exchanger and use a summer block when it’s warm. The system has a small heat pump that helps with warming the sub-zero air in winter.

We both have reach the same conclusion and I note it’s much harder to close an external door if all windows are closed.

 

[WannabeOwner]

The passivhaus rated unit we chose, silencers and ducting is taking up half of our attic.

MVHR is huge - the unit, the pipes, everything. Its one of the reasons why I think retrofit is really hard and, consequently, what a pity that this is not the building standard for New Build. Until we build to that standard then in order to achieve Net Zero CO2 the housing stock will need upgrading ... and its blinking hard (and expensive) - and therefore unlikely to happen.

Knock-down and rebuild is much easier (probably cheaper), but a dreadful choice

Routing even the pipes we do have was frankly hell.

Us too (in the old bit where we retro fitted). Luckily previous owner had installed large fitted wardrobes in every bedroom - so we stole some space from those to hide pipes from Attic to Ground floor room below. Bungalow would be easier as a ceiling vent in each room can be accommodated from attic

In summer we aren't getting the full benefit as we still have all the windows down

I am guessing your rooms are internally insulated (rather than the building externally wrapped)? An option might be to have portable Air Con unit in the room (or the main room) and stuff the hose out the window and block up the gap - which is a bit more difficult for hinged windows (but kits are available), especially if you have excess PV so that it is cost neutral to run. MVHR will move that cold to other rooms (or reduce exhaust temperature and thus DeltaT to incoming air and "recover more")

I know you know this but the moment you open the windows in Passive Haus you are letting in heat (or cold), pollen, dust, flies etc. Its fine to do that, if your want to for whatever reason, just better not to - the ventilation provides loads of air changes (half the air in the house is replaced every hour)

I presume your MVHR has "bypass" - so as soon as evening temperature is lower than house the recovery is bypassed and the cool air pushed straight into the house. There is a min temperature at which the bypass closes and heat recovery starts again.

My Air Con is retro-fit and a compromise (wish it had been in original design), so we open windows in evening and early morning to cool the thermal mass. But that also lets in flies and pollen, so I am looking at upgrading the "cooling" so we don't have to do that. Our MVHR pipes are not insulated (and can no longer be accessed easily), so I don't have the option to cool the MVHR air and I don't want ugly individual air con units in each room, so my planned route is to use cold water through UFH. Heating people tell me it won't work because it will create condensation on floor etc. etc. but they just don't understand how little heat actually needs to be removed - my plan is to try UFH water a few degrees below ambient and see how that works

The only reason I need this at all is my "Mock Georgian" build doesn't have any roof overhangs and a large bay window with glass on East, South and West ... but that said even with temperature in high 30's my room temperature is not above 23C during the day; night venting is just to remove heat from the thermal mass otherwise we would get cumulative increases day-on-day during a heatwave - and built-in Air Con cooling (or roof overhangs) would have solved that - if only the expensive professionals we used had thought to mention it! (My internal walls are all dense-block for highest thermal mass - brickies hated me humping them about ...)

I think this is a problem with Passive Haus - owner wants some "vanity features" and architect / technician has to accommodate them and offset somewhere else which impacts the actual day to day operation of the building.

 

[Avendit]

I am guessing your rooms are internally insulated (rather than the building externally wrapped)? An option might be to have portable Air Con unit in the room (or the main room) and stuff the hose out the window and block up the gap - which is a bit more difficult for hinged windows (but kits are available), especially if you have excess PV so that it is cost neutral to run. MVHR will move that cold to other rooms (or reduce exhaust temperature and thus DeltaT to incoming air and "recover more")

I know you know this but the moment you open the windows in Passive Haus you are letting in heat (or cold), pollen, dust, flies etc. Its fine to do that, if your want to for whatever reason, just better not to - the ventilation provides loads of air changes (half the air in the house is replaced every hour)

I presume your MVHR has "bypass" - so as soon as evening temperature is lower than house the recovery is bypassed and the cool air pushed straight into the house. There is a min temperature at which the bypass closes and heat recovery starts again.

I think this is a problem with Passive Haus - owner wants some "vanity features" and architect / technician has to accommodate them and offset somewhere else which impacts the actual day to day operation of the building.

Thanks. Do you know if there is a detailed description of how bypass is supposed to work somewhere? We have ours set to 'keep rooms at 18' and still feel we have to manually bypass every day for 24 hours. If I understood better what it was trying to achieve, rules for opening/closing etc, we could probably optomise this. Its a zhender comfoair unit if that matters.

I'm aware of the problems of openeing windows, having trouble convincing the rest of the family. The bigger problems is really the heat coming from windows. The picture windows have been massivly improved with external blinds this year, and in a few weeks we are getting solar film fitted to the other 2 problem windows upstairs. Fixing the picture windows has helped cool the whole house, and I'm hoping the film is enough to make the problem effectivly go away. I would have loved to do proper shutters, but the shape of the house wasn't going to work.

The big picture window is unfortunetly in the least good place for the MVHR as we had the opposite of you and didn't design it in the extension (ran out of budget at that point) and it turned out there was just no way to get pipes into it retrospectivly - stupid steel beams. Its open plan, but does mean its sharing a single supply vent for a really quite large area. Plenty for fresh air supply, not so great for removing heat.

Intersting with the aircon - we do have a portable aircon unit, only needed it once so far this year and the MVHR did seem to help it be effective. Should the rule be aircon on, house sealed, MVHR set to recover, and it will know to 'recover' the cool?

 

[MrBadger]

Do you know if there is a detailed description of how bypass is supposed to work somewhere? We have ours set to 'keep rooms at 18' and still feel we have to manually bypass every day for 24 hours. If I understood better what it was trying to achieve, rules for opening/closing etc, we could probably optomise this. Its a zhender comfoair unit if that matters.

We have a Vent Axia system. Off top of my head, Summer Bypass (we also have option of an evening boost) kicks in when within the unit, temperature of incoming air is cooler than temperature of exhaust air AND temperature of exhaust air is above a certain temperature, in our case 23C. The latter prevents comfortable air being replaced with 'cold' air. When summer bypass is activated, it effectively bypasses the heat exchanger.

The important thing to remember is that the volume of air being exchanged by an MVHR system is tiny compared to that needed to actively warm or cool. We once had a warm air heating system which contrary to popular belief was very effective and the size of the ducting was many orders of magnitude larger than the working/balanced area of even a double ducted MVHR vent. An MVHR system does an excellent job at maintaining temperature, but its not going to warm or cool very quickly. Even in <0C winter, if we run a purge (100% fan) for several hours, whilst we can detect room temperature dropping, its very slow and minimal impact, and thats with a potential 20C delta between incoming out exhaust temperature. With summer bypass, that delta will be much less. Summer bypass helps a bit, bit its not going to be providing large amounts of cooling.

Biggest advantage of MVHR in hot summer is being able to keep everything closed and maintain high quality air. We often have 10-15C delta between inside and out depending on how long the thermal mass has been heated. But it is nice to throw windows open at start and end of the day (when outside is cooler than inside) to take advantage of a cool breeze, even if it sometimes smells of wet badger...

 

[RedMod3]

I am unsure why any particular brand of energy efficient housing standard is being plugged.

The key is very low u values for all floors, ceilings and walls, adequate ventilation with heat recovery and energy efficient appliances while all the time considering the sun and means of storing solar.

There are many ways to skin a cat, and I’ve chosen my own way that is efficient, cost effective and yields good results.

 

[WannabeOwner]

how bypass is supposed to work

My understanding matches @MrBadger

Bypass ... kicks in when within the unit, temperature of incoming air is cooler than temperature of exhaust air AND temperature of exhaust air is above a certain temperature, in our case 23C

I can hear the motorised "flap" move, and it does that back-and-forth a fair bit (it has done it just now, at 11AM on a fine sunny day ... no idea why ... maybe outside air has been cold enough until just now - I suppose under 20C would be "cooling", so maybe 11AM is about right).

I suspect I have the hysteresis set too narrow-band on mine, either that or the sensor is too close such that when the flap opens the temperature changes so suddenly that the sensor (wrongly) reacts, and that is why I hear it going back-and-forth over a period of time. Maybe it is supposed to work like that.

The other thing to consider is insulating the MVHR unit itself. Is it, perhaps, picking up temperature from its surroundings (hot attic in Summer, cold attic in Winter) and that is soaking into the heat exchanger? I presume all your pipes in loft are insulated? This isn't going to fix sun shining straight onto glass windows of course ... but if not already done it will improve MVHR efficiency.

Should the rule be aircon on, house sealed, MVHR set to recover, and it will know to 'recover' the cool?

My aircon comes on when PV is exporting (more correctly it comes on in morning as soon as PV generating more than house usage IF the day looks like the PowerWall will get to 100% during the day). It services only part of the passive haus part (which is also the part that does get direct sun), but that is enough to combat the heat increase from the direct sun, and MVHR transfers that cooling effect elsewhere such that we don't have to do anything in other rooms.

My guess is if we didn't Air Con cool that main room it would get "uncomfortably hot" and that would, in turn, mean that the DeltaT in Heat recovery was too high, and thus incoming air would not be cooled sufficiently ... and the outcome would be that all the rooms would therefore warm up.

Its entirely my fault for insisting, at design phase, that we have an exposed (no overhang) bay window with glass East, South and West making sure that there is glass in direct sun all day long

An MVHR system does an excellent job at maintaining temperature, but its not going to warm or cool very quickly

I think in Passive Haus the heating / cooling energy requirement is so low that it then becomes possible to use MVHR for "delivery".

I've had a number of discussions with a passive haus consultant on this (basically discussing how I could, retrospectively, improve mine). The MVHR pipes (within the house, let alone "in attic") would need to be insulated, otherwise the cooling would make the first few metres of metal pipe cold, and cause condensation (with all the problems that entails), and the cooling effect would not actually reach the rooms. Mine aren't insulated (and now very hard to get to), so that's not an option for me.

For a new-build / new-install the MVHR pipes (internal within the house, let alone attic etc.) could be insulated, such that Air Con (and heating) inline in the MVHR would transmit that heat to the rooms. Passive Haus is 10W/sq.m. peak - average sized living room in UK is 17sq.m. so that room would need a 170W heater when it is "cold outside", hence why I think that could be delivered by MVHR pipework.

 

[WannabeOwner]

I am unsure why any particular brand of energy efficient housing standard is being plugged.

This is my understanding:

"close to Passive Haus" does not get you the benefit. I don't fully understand the physics but that is something like "Once you get to mega-insulated any 'fault' has a, relatively, massive impact".

So if you don't quite have enough air tightness, or you have a little bit of cold bridging, or fall a bit short on U-Values, the impact is surprisingly dramatic.

In Passive Haus the aim is that the building achieves the air tightness and peak heat (cooling) requirements. There are some fancy calculations ("PHPP") which enable that to be calculated, based on U-Values of all the materials used, and backed by scientific research over many decades. So if you want a particular feature, and that has bad u-value, that can be compensated elsewhere until the PHPP numbers are OK.

If, like me and I suspect many other owners, you insist on "A big picture window", or "I need to save some money on THAT insulation" then you don't achieve the full gain.

I'm sure still very comfortable, but missing some benefits. If you cannot control the heat gain ... because the insulation is "a bit less" than PHPP, then in a heatwave the temperature will climb day-on-day .. .and then you have to throw open a window at some point, and that lets more heat in ... and then you are back to conventional building style of living. It would still be very comfortable, but @Avendit and I are saying "Wish we had got it right first time" (and I would say "Wish I had been better advised")

I also don't know at what point the health benefits start ... Passive Haus is recognised as making a large different to people with respiratory problems (Asthma and up). I don't know how much of that is just having mechanical ventilation, and pollen filters. But if you have to open a window, because the room is too hot, obviously that benefit goes away. So getting the insulation to the point where you don't need to open a window means you have the air quality.

Personally I think there is also benefit in the even temperature. I no longer need to put a sweater on in winter, but I used to "before". That meant my body had to work harder in the winter. That's also the case if there are mould spores in the house. The body will have to take energy /resource from somewhere else - and if that is the immune system then less ability to combat infection in the early stages.

The point I made, up thread, was my wife and I have had no winter cough / colds since moving in half a dozen years ago, whereas we did have every winter before that, and my wife was working in an open plan office with people around her having the normal winter colds / flu etc, This is a known benefit, but was not known to us when we did it - it was only when Passive Haus guy asked me, several years after moving in, that he then said "Known benefit" - as such I haven't imagined that!

 

[WannabeOwner]

P.S. I found this book helpful when we started. It is written for both lay person and also has technical panels for people who want to see the maths etc.

The Passivhaus Handbook: A Practical Guide to Constructing and Retrofitting Buildings for Ultra-Low-Energy Performance

 

[Avendit]

Passivhaus just has the brand recognition, and in addition to the above points has the training and certification processes nailed. A big problem with current building regs is that they inspect some, test others and so on, ends up with a performance gap pretty often. Passivhaus has that all sorted.

The Scottish proposal I linked above does say 'pasivhais-like' standard, probably accepting some changes to the regime (rather than design principles) that make it more deliverable at nation scale.

 

[WannabeOwner]

A big problem with current building regs is that they inspect some, test other

This is crazy - some lobbying of government, by building companies, allowed it presumably. "We've done an air test of one house, all the others the same will be identical"

The air pressure test is designed to find if there is a problem, so it can be rectified. Not doing the test allows sloppy building practices to carry on unchecked. Building a modern, well insulated, building requires attention to detail - way more than anything the Victorians had to worry about - some of which are very hard to fix after-the-fact e.g. taping of boards that are then covered and no longer accessible.

My air test revealed that there was a missing seal in one window. The site manager was mortified ... I was thrilled. If that had not been found we would have just assumed that that bedroom "was a bit cold", and it would have seriously eroded our heat recovery efficiency ... and adversely impacted our heating bills - forever!

 

[Artiste]

I’ve gone the opposite way. I live in a farmhouse in a rural location. I like to hear the sound of rain, and to smell freshly cut grass and wild flowers. This means that in summer nearly all the windows are open, letting in untold numbers of undoubtedly deadly microbes, pathogens and allergens. The thick stone walls keep the place cool. Hot water and heating in winter are provided by a boiler heated by a huge fireplace in the living room and with logs from my own wood. My bedroom window is wide open every day of the year and there is no heating in there, so in winter I sometimes have two thick quilts on the bed. It isn’t doing me any harm - I haven’t had a day off work in 20 years and I haven’t seen my GP for 10 years, and that was only because she insisted I come in for a health check.

People’s lack of exposure to bacteria and viruses actually means their immune system becomes weaker and less effective, as was caused in nearly everyone during lockdown. Allergies are increasing massively because people are not exposed to potential triggers when they are young. The cleaner the environment, the weaker the immune system and the greater the risk of allergies. So embrace all these lovely viruses, bacteria and allergens and, in the long term, lead a healthier life.

 

[Pants]

Isn’t this thread supposed to be about commando sockets and UMC?

 

[Avendit]

I’ve gone the opposite way. I live in a farmhouse in a rural location. I like to hear the sound of rain, and to smell freshly cut grass and wild flowers. This means that in summer nearly all the windows are open, letting in untold numbers of undoubtedly deadly microbes, pathogens and allergens. The thick stone walls keep the place cool. Hot water and heating in winter are provided by a boiler heated by a huge fireplace in the living room and with logs from my own wood. My bedroom window is wide open every day of the year and there is no heating in there, so in winter I sometimes have two thick quilts on the bed. It isn’t doing me any harm - I haven’t had a day off work in 20 years and I haven’t seen my GP for 10 years, and that was only because she insisted I come in for a health check.

People’s lack of exposure to bacteria and viruses actually means their immune system becomes weaker and less effective, as was caused in nearly everyone during lockdown. Allergies are increasing massively because people are not exposed to potential triggers when they are young. The cleaner the environment, the weaker the immune system and the greater the risk of allergies. So embrace all these lovely viruses, bacteria and allergens and, in the long term, lead a healthier life.

There is a balance to be struck to be fair. Problem is, not everyone has enough land to grow their own firewood. Most of the UK used to be wooded etc etc etc.

Isn’t this thread supposed to be about commando sockets and UMC?

shhh! you'll ruin the fun! (UMC discussions probably better adding to the old thread so its all in once place anyway?)

 

[WannabeOwner]

Isn’t this thread supposed to be about commando sockets and UMC?

Yes

I did propose an alterative thread back in post #73, but ...

I'd be happy to participate in other threads on the subject if folk are interested, or MOD could perhaps split this one?

 

[RedMod3]

P.S. I found this book helpful when we started. It is written for both lay person and also has technical panels for people who want to see the maths etc.

The Passivhaus Handbook: A Practical Guide to Constructing and Retrofitting Buildings for Ultra-Low-Energy Performance

Do you get paid for promoting Passiv Haus?