Are you pleased with your MHVR or an expensive white elephant?

[Haku]

1 hour ago, jack said:

 

It'll have very little impact on overheating unless you install some sort of cooling coil (driven by an ASHP).

 

It does help slightly when it's very hot, by helping to maintain any temperature difference between inside and out. That can be useful if you're using aircon, in particular.

Thanks. Overheating is my main area of concern - MHVR may not be the solution to my issue. 

[SteamyTea]

1 hour ago, Nickfromwales said:

Keep an eye out. Sabre- toothed tiger seen loose in your area. Be on high alert 

And here I am.

Do you think it is tight to build to a minimum standards when you know there are improvements that can realistically, only be put in economically at the initial design and build time.

Those houses are going to be around till well after your grandchildren have spent their inheritance.

[Nickfromwales]

1 hour ago, Haku said:

Thanks. Overheating is my main area of concern - MHVR may not be the solution to my issue. 

Mitigation by design will be your friend here. Solar reflective glazing is a good ally, so are blinds / canopies etc.

[Nickfromwales]

39 minutes ago, SteamyTea said:

when you know there are improvements that can realistically, only be put in economically at the initial design and build time.

Which is where we come in  

Fabric first approach every time, but a commercial concern won't always "do the right thing" as that isn't necessarily what is sets out to achieve.

Whilst British BRegs are still so utterly dogshit, we cannot complain to those taking advantage of it. Sad, but true ( honest ). 

[Oz07]

Companies building to the regs aren't taking advantage of anything. They're building a house to the regs the govt sets out. Why the hell would they build passive it's such a niche market most homebuyers won't even know what it means. 

[joe90]

Most people don’t even take any notice of the SAP rating for the houses they buy!!!

[Bitpipe]

If the average person is not that bright then 50% of the population is dimmer than that.

 

I think the comments above say it all really. If your house is well insulated and reasonably airtight then MVHR makes sense as you get good ventilation 24/7 and in an energy efficient manner (not loosing warm air you paid to heat).

 

Yes you can open windows as much as you like, no MVHR will not noticeably heat or cool your house..

 

Will a buyer pay more for it? Almost certainly not but then you can say the same for most of the building fabric that contributes to its performance.

 

5+ years in a near passive house with MVHR and perpetually open doors for teenagers and dog.

 

Overheating will make those houses uncomfortable to live in though - you need to mitigate that before considering anything else.

 

[Oz07]

9 minutes ago, Bitpipe said:

Will a buyer pay more for it? Almost certainly not but then you can say the same for most of the building fabric that contributes to its performance.

So if the govt doesnt regulate for it and the market doesnt demand it, why do people get upset when the builders don't build it!?

 

To be honest I don't think you can call the average buyer stupid for not knowing or caring about it. Life is short at the end of the day

[tonyshouse]

Would not be without mine 

[MikeSharp01]

Given the rate of adoption of electric cars, and the fact there will be no choice in about 10 years I cannot help thinking it wont be long before HMG see the writing on the far to poorly insulated walls about where all the carbon is coming from and set the standard in the right place thus making passive a household name. 

[Oz07]

36 minutes ago, MikeSharp01 said:

Given the rate of adoption of electric cars, and the fact there will be no choice in about 10 years I cannot help thinking it wont be long before HMG see the writing on the far to poorly insulated walls about where all the carbon is coming from and set the standard in the right place thus making passive a household name. 

I remember Jeremy saying 10 years ago the govt couldn't control energy prices. He might of been right but till you see energy prices double or maybe triple nobody normal is going to prioritise passive 

[Oz07]

Actually thinking about it didn't our Theresa bring in a cap on energy prices?

[MikeSharp01]

Its not about energy prices its about the damage to the planet - with luck the groundswell will force it. 

[Oz07]

20 minutes ago, MikeSharp01 said:

Its not about energy prices its about the damage to the planet - with luck the groundswell will force it. 

Maybe. Remind me what % UK contributes to carbon emissions let alone home energy usage 

[Haku]

28 minutes ago, MikeSharp01 said:

Its not about energy prices its about the damage to the planet - with luck the groundswell will force it. 

Absolutely agree....but if you have to value ROI and are already building at a uValue above the regs requirement, installing ASHP & car charging points how much more should a developer do. None of these things add much value from a  buyers perspective but from a responsible developer perspective I want to build sustainable homes because that is the right thing to do. MHVR seems to be a small incremental gain from an eco perspective and wont pay for itself over its lifetime so then it comes back to does it improve living conditions sufficiently to justify the time & cost of installation. So far it seems to be a bit like Marmite!

[andy]

2 hours ago, Oz07 said:

So if the govt doesnt regulate for it and the market doesnt demand it, why do people get upset when the builders don't build it!?

Because the government are bowing to the selfish, short term demands of the building companies lobbying... and/or are benefiting themselves from this.

 

Building regs should be forcing everything built now to be passive standard but alas I don’t see that happening anytime soon, just pathetic stunts like the recent green grants nonsense.... irks me somewhat you could say ?

[Oz07]

I've got one myself but I think a lot of buyers can't help bit justify it After spending a few grand!

 

Not all builders are lobbying the govt. Maybe a few big nationals but I bet there are hundreds of regionals. We haven't got the skills to be mass passive builders atm end of. 

[SteamyTea]

1 hour ago, Oz07 said:

Actually thinking about it didn't our Theresa bring in a cap on energy prices?

Which has, so far, managed to increase prices rather than lower them.

All that happened was the top price is capped (based on general inflation and bulk energy prices).  So to counteract this, the companies upped the lower and mid tier prices.

[Oz07]

1 minute ago, SteamyTea said:

Which has, so far, managed to increase prices rather than lower them.

All that happened was the top price is capped (based on general inflation and bulk energy prices).  So to counteract this, the companies upped the lower and mid tier prices.

? cry to me when you struggle to heat your house.

[SteamyTea]

25 minutes ago, Oz07 said:

Maybe. Remind me what % UK contributes to carbon emissions let alone home energy usage 

All depends how you want to measure it?

 

[Iceverge]

@Haku

 

Trickle vents and extractor fans have a poor record of maintaining an acceptable level of air quality. 

 

Over ventilation in windy weather cools the house and occupants close window and wall vents. Noisy extractor fans get turned off. This is seldom rectified in still weather leading to high humidity, high CO2 and high VOCs through under ventilation. Poor occupant health and decaying buildings are the ultimate result.

 

In essence it is a manually controlled system. It can work with very diligent house owners who have appropriate knowledge and time to alter the vents as required. Unfortunately most people don't understand and don't have the time 

 

The simple answer is continuous mechanical ventilation of some sort.  This can suck out blow in or both. Simply replacing basic extractor fans with humidity controlled ones which run at a low level 24/7 is only a small price increase but will make a noticeable difference. No maintenance or knowledge required. We used to run the kitchen extractor in our old rental cottage when we were out. It made a measurably difference to mould and damp. 

 

Remember, as a developer,poor ventilation also makes sick buildings and you're more likely to have call backs from your new neighbours if you don't take care of it at construction.

 

We installed MVHR. Cost <€3k Inc vat for 186m2 DIY. Wouldn't be without it. No cold spots, no drafts. No noise from outside. 

 

TLDR. 

 

Natural ventilation doesn't work in practice. 

 

Continuous Mechanical ventilation keeps occupants and buildings healthy. 

 

MVHR does the above, improves comfort and saves energy

[Oz07]

As a developer might be worth checking out PIV @Ferdinand has 1 or 2 in his rentals

[Bitpipe]

11 hours ago, Oz07 said:

 We haven't got the skills to be mass passive builders atm end of. 

 

Well the one way to address that is to change the standards and then the skills will follow.

 

Sad fact is most volume house builders have made their profit when planning is granted and everything from there on in is a cost to be reduced.

 

Usually only 1:10 builds is inspected by BC (I got this figure direct from a BC themselves) so if that one barely passes then god knows what state the others are in.

 

SAP has helped to a degree but we've all seen new builds with 'bolt on green' like solar thermal that the householders likely do not understand either.

 

As a nation, we're not very environmentally literate - we like nature and the countryside and tut at litter and fly tipping but won't learn how to reduce energy consumption at home unless it's really hitting us in the pocket.

[Ferdinand]

I honestly don't know how I'd call it in a new development.

 

I use a PIV, sometimes with one or two HR trickle fans, to make sure that when renovating leaky old houses to be more airtight there is a degree of resilience against tenants who choose damp lifestyles.

 

Obvs as good as possible fabric - on insulation and leakiness - is the start.

 

If MVHR is a no go (after checking what it would if put in at design stage) then I think I would provision design and wiring for PIV and HR trickle fan. Probably it makes sense to put the fans in loo / bathroom anyway as something is needed, and leaving a gap under the doors to ensure circulation. And then take a view.

 

F

[SimonD]

16 hours ago, Haku said:

MHVR seems to be a small incremental gain from an eco perspective and wont pay for itself over its lifetime so then it comes back to does it improve living conditions sufficiently to justify the time & cost of installation. So far it seems to be a bit like Marmite!

 

Well, I'm one of those opting not to go for MVHR. Having done plenty of research on ventilation, there's still lots to learn about the whole subject when it comes to domestic properties. There are also lots of myths about the effectiveness of natural ventilation (I suspect often perpetuated by the marketers of MVHR system makers). This goes for the eco perspective too.

 

When it comes to MVHR location is often overlooked. If I was back up in the north of Sweden building a house, MVHR would be high on my list due to the very long and cold winters. Down here it the southwest of England it's a very different matter because the climate is so mild.

 

Here is a piece of fairly recent research suggesting similar. In this study, they used two new passivhaus flats built in Cardiff. One used MVHR and the other natural ventilation. The naturally ventilated flat consumed 36 kWh primary energy/m²a less than the flat with MVHR with no reduction in indoor air quality or comfort. A Natural Ventilation Alternative to the Passivhaus Standard for a Mild Maritime Climate

 

At the end of the day there are plenty of studies looking at problems associated with MVHR but there are also issues with natural ventilation where it hasn't been thought through or implemented properly either.

 

 

 

Edited March 14, 2021 by SimonD