MVHR and windows open

[Redoctober]

18 hours ago, mjc55 said:

Resurrecting an old thread here but it does focus on something we have been thinking about.

 

We have always (40+ years) slept with the window open at night (apart from the odd occasion when the rain was horizontal!) and embarking on our build leads me to question how this will work with MVHR?

 

 

 

Hi @mjc55 When we embarked on our project 6 years ago I too came aross the dilemma you are currently pondering. I have never experienced  life within a house that has such a system installed so I suppose at the time, it was a case of what you haven't had you won't miss.

 

But for us, it came down to "budget" restraints and I suppose that was the over riding reason we chose not to have one installed. Something[s] had to give. Everyone undertaking their own project I suspect, comes across this issue. 

 

Anyway, six years on - do I regret it - no - we are comfortable living in our air tightish house - 4.90 - achieved on our air tightness test - 

 

We have our windows open at night other than when the rain is coming in horizontally and the wind is trying to remove our roof🤣

 

If I was to go again, and that is never going to be the case, I would consider installing an MVHR if funds allowed, given the experience of others on this site alone. 

 

Hope this helps. 

[ToughButterCup]

Budget constrains us too. ( @Redoctober )

 

3 years living in an also  air-tightish house, no MVHR. Double sliding windows (4.5m) fully open every day the wind direction allows - no point in MVHR or air-tightishness for that matter. 

 Once the air temperature is above 15 the slider is open all the time . So the MVHR - when fitted - will be OFF for 4 months of the year. We also sleep with our suicide windows open (glass door with glass Juliet balcony)

 

Still sucking my teeth a bit about the expense of MVHR . But we know we can wait for prices to come down and performance to improve. The comfort afforded by Passivhaus design is very noticeable - we still pop round into our 1800- built cottage nextdoor. More for the pleasure of a roaring open fire . The contrast - the unreactiveness of our build is the most noticeable thing. 

 

SWMBO makes a simple point: why buy MVHR when it's not going to be used for half the year? She listens politely to the answer. Smiles, and looks away.

[Adrian Walker]

On 14/04/2024 at 15:30, ToughButterCup said:

 

 

SWMBO makes a simple point: why buy MVHR when it's not going to be used for half the year? She listens politely to the answer. Smiles, and looks away.

 

Isn't it better to be happy for 12 months rather than just six?  I put my winter clothes & duvet away for 6 months?

[joe90]

But no two houses/builds react the same to “weather/temps” as no two “people” react to the conditions the same. I remember Jeremy going into minute detail of local weather patterns, designing his own weather curves etc etc   But in the end he scrapped it and fitted a single room stat but he still found he needed more cooling than heating which nothing predicted for him. I liked the MVHR I fitted and the house had an airy feel even with all the windows shut, however during warm weather and doors and windows open I would switch it off. I wanted to run it on a CO (is that right Nick?) monitor to detect stale air but was told they are expensive and not that reliable so I ran it on a humidity sensor.

[dpmiller]

If you don't use a prepared for- or installed- MVHR how do you deal with humidity and "odours" in the wetrooms?

[mjc55]

1 hour ago, ToughButterCup said:

Budget constrains us too. ( @Redoctober )

 

3 years living in an also  air-tightish house, no MVHR. Double sliding windows (4.5m) fully open every day the wind direction allows - no point in MVHR or air-tightishness for that matter. 

 Once the air temperature is above 15 the slider is open all the time . So the MVHR - when fitted - will be OFF for 4 months of the year. We also sleep with our suicide windows open (glass door with glass Juliet balcony)

 

Still sucking my teeth a bit about the expense of MVHR . But we know we can wait for prices to come down and performance to improve. The comfort afforded by Passivhaus design is very noticeable - we still pop round into our 1800- built cottage nextdoor. More for the pleasure of a roaring open fire . The contrast - the unreactiveness of our build is the most noticeable thing. 

 

SWMBO makes a simple point: why buy MVHR when it's not going to be used for half the year? She listens politely to the answer. Smiles, and looks away.

 

You do seem to be very similar in ideas to the way we work Mr ButterCup, noticed this in other threads that we have partaken in! 

 

I suppose though that having it installed but not using it to it's fullest capabilities doesn't have many downsides other than cost?

 

Our plan is to have large opening windows and I would fully expect these to be open for as much time as possible.  We are planning on pretty big overhangs over the rear elevation so even in rainy weather there would be the opportunity to sit on our "Veranda".

Edited April 14 by mjc55

[mjc55]

4 minutes ago, dpmiller said:

If you don't use a prepared for- or installed- MVHR how do you deal with humidity and "odours" in the wetrooms?

I guess (but am prepared to be contradicted) that opening a window would work!  Something we did in our previous house for 20 odd years without ever having condensation or mould problems in our en-suite or bathroom.

[Simon R]

11 minutes ago, joe90 said:

he still found he needed more cooling than heating which nothing predicted for him. I liked the MVHR I fitted and the house had an airy feel even with all the windows shut

I found the same with our build. Heating was a problem that wasn't predicted by our SAP calcs. Fitting an MVHR is a expensive but it does provide a very comfortable living environment in both winter and summer. The energy conservation is a factor year round. Typically our input/output air temperatures are within about 1.5C so in winter with the outside air temperature down at 5C and the house running at 22c the incoming air into the house is at 20.5C having been heated by the outgoing air at 22C. In summer with the A2A cooling on the house is still at 22C with the outside air temperature up to 28C the outgoing air is cooing the incoming air to 23.5, not a lot but it all helps. I was initially concerned over the operation of summer bypass, but it's easily disabled.

It's all about saving energy. I'm not sure what the payback period is like but purely in terms of a comfortable environment I'd not want to be without an MVHR.

[joe90]

52 minutes ago, Simon R said:

I'm not sure what the payback period is like but purely in terms of a comfortable environment I'd not want to be without an MVHR.

I am not sure “payback period” is that relevant for MVHR if its prime function is comfort and we are willing to pay for it. 🤷‍♂️

[Bonner]

I see a few mentions of the expense of MVHR. I self installed a simple system complete for less then £1500 in a 260m2 house. It has no sensors just manual boost which we use occasionally, otherwise it stays on trickle rate 24/7, even when some doors and windows are open. Really happy with the air quality (which I monitor with sensors), best value for money in the whole project and a no brainer in a new house IMO.

[MikeSharp01]

On 15/03/2022 at 18:21, JohnMo said:

No particular warning on my Titon units

Any long term issues with the Titons, we are just about to order the new 4B eco plus?

[JohnMo]

10 minutes ago, MikeSharp01 said:

Any long term issues with the Titons, we are just about to order the new 4B eco plus?

I bought my two units as new (other) units on eBay, one came with a faulty fan motor. Titon were great, although out of warranty, they helped identify the issue supplied parts etc, at my cost. Now been running for a couple of years no issues.

 

Like that you can speak technical to someone in the UK, get the parts quickly and easily.

[MikeSharp01]

8 minutes ago, JohnMo said:

 

Like that you can speak technical to someone in the UK, get the parts quickly and easily.

Yes the technical guy I have been speaking to took me through all the details and advised me on flow rates, silencing, back pressure calculations etc. Really helpful.

[TerryE]

On 14/04/2024 at 15:30, ToughButterCup said:

SWMBO makes a simple point: why buy MVHR when it's not going to be used for half the year?

 

You could make the same point about the central heating.  Is that as valid?

 

We fitted our MVHR ourselves. It cost us less than £3K, IIRC.  When I did the heating calcs the air recirc losses on the top 2 floors meant that we would have definitely needed some form of central heating solution for these upper floors  without it.  This would have cost us a lot more than the install cost of the MVHR. 

 

We just leave ours running 24 × 365.  The running cost is in the noise compared to the heat recovery energy savings during net heating days.  And as @dpmiller points out: fresh air and no damp year-round.  And yes, in the summer we open windows as and when desired or needed.  The MVHR still keeps the wet rooms and unused bedrooms fresh.

 

Edited April 15 by TerryE

[JohnMo]

I have just been away since Thursday visiting. Was like a breath of fresh coming home, light, fresh airy feel, as soon as you walk in the door.

 

Good old MVHR.

[NSS]

We're not passive, but pretty well insulated and achieved 1.6 on the air test. We have had our MVHR running 24/7/365 for over 6 years now (except when changing filters). We have one program for winter, and one for summer, and we occasionally put the boost on (to clear cooking smells a little faster).

 

We never open windows. Doors are for going through and closed immediately. Excellent air quality was the primary goal, and that's exactly what we have. What's more, not only have we never had a musty smell, never mind any mould, but the house stays virtually dust (and allergen) free. Best of all, and despite a degenerative lung condition, my wife is still enjoying better health than she did prior to living here.

 

We wouldn't, and she probably couldn't, live in a home without MVHR ever again.

[Nickfromwales]

On 14/04/2024 at 16:58, mjc55 said:

 

You do seem to be very similar in ideas to the way we work Mr ButterCup, noticed this in other threads that we have partaken in! 

 

I suppose though that having it installed but not using it to it's fullest capabilities doesn't have many downsides other than cost?

 

Our plan is to have large opening windows and I would fully expect these to be open for as much time as possible.  We are planning on pretty big overhangs over the rear elevation so even in rainy weather there would be the opportunity to sit on our "Veranda".

Heat recovery all winter?!?!

Why bother making an airtight house if you don't intend to install MVHR? Why bother installing it if you don't use it? And how the feck does anyone expect to get a sign-off from the BCO if you haven't installed mechanical extractor fans in each bathroom / utility / kitchen whilst you think it over?

 

In rainy seasons you'll be importing humid / damp air and this will be trapped within the fabric of your build when you do finally shut up shop to go to sleep. Open windows all day every day and whenever in-between, but, when you close the house up, MVHR will come into its own.

 

 

 

On 14/04/2024 at 17:00, mjc55 said:

I guess (but am prepared to be contradicted) that opening a window would work!  Something we did in our previous house for 20 odd years without ever having condensation or mould problems in our en-suite or bathroom.

Which I'm guessing was drafty and inefficient with poorly installed 2G glazing etc, ergo it had a high rate of natural infiltration and mechanical fans plus trickle vents maybe? 

[Nickfromwales]

On 14/04/2024 at 17:58, joe90 said:

I am not sure “payback period” is that relevant for MVHR if its prime function is comfort and we are willing to pay for it. 🤷‍♂️

There is a significant saving via the HR element  

[ToughButterCup]

On 14/04/2024 at 16:58, mjc55 said:

 

You do seem to be very similar in ideas to the way we work Mr ButterCup, noticed this in other threads that we have partaken in! 

 

I suppose though that having it installed but not using it to it's fullest capabilities doesn't have many downsides other than cost?

 

Our plan is to have large opening windows and I would fully expect these to be open for as much time as possible.  We are planning on pretty big overhangs over the rear elevation so even in rainy weather there would be the opportunity to sit on our "Veranda".

 

I thought these photos might interest you ..... the first one taken a few minutes ago

The slider in the kitchen has been open all morning - right hand side of the image is to the North, and thus the Winter Garden is in wind shadow (wind NW) , but in full sun (it was raining when I took the photo)

 

 

There is a 2.5 meter overhang for a 'veranda' shown here earlier in the build. We call it a Winter Garden - yet to have anything in it , but won't be long now.

SWMBO intends to fill it with - knowing her - a jungle or as close to that as she can get. There's one episode of Grand Designs where Kevin WotHisFace showed a similar design, but he calls the area a Breeze Corridor.

The look of triumph on Debbie's face was a picture. First time she'd ever been 'on trend' she remarked.

 

[mjc55]

4 hours ago, ToughButterCup said:

 

I thought these photos might interest you ..... the first one taken a few minutes ago

The slider in the kitchen has been open all morning - right hand side of the image is to the North, and thus the Winter Garden is in wind shadow (wind NW) , but in full sun (it was raining when I took the photo)

 

 

There is a 2.5 meter overhang for a 'veranda' shown here earlier in the build. We call it a Winter Garden - yet to have anything in it , but won't be long now.

SWMBO intends to fill it with - knowing her - a jungle or as close to that as she can get. There's one episode of Grand Designs where Kevin WotHisFace showed a similar design, but he calls the area a Breeze Corridor.

The look of triumph on Debbie's face was a picture. First time she'd ever been 'on trend' she remarked.

 

Looks fab Mr ButterCup 😁

[mjc55]

18 hours ago, Nickfromwales said:

Heat recovery all winter?!?!

Why bother making an airtight house if you don't intend to install MVHR? Why bother installing it if you don't use it? And how the feck does anyone expect to get a sign-off from the BCO if you haven't installed mechanical extractor fans in each bathroom / utility / kitchen whilst you think it over?

 

In rainy seasons you'll be importing humid / damp air and this will be trapped within the fabric of your build when you do finally shut up shop to go to sleep. Open windows all day every day and whenever in-between, but, when you close the house up, MVHR will come into its own.

 

 

 

Which I'm guessing was drafty and inefficient with poorly installed 2G glazing etc, ergo it had a high rate of natural infiltration and mechanical fans plus trickle vents maybe? 

 

In 20 odd years living there we didn't find it draughty at all.  

 

Inefficient, need to understand how you quantify that I guess. The house had been completely gutted and timber DG windows installed when we bought it in 99.

 

Did have a mechanical fan in our en-suite, stopped working years ago and didn't bother fixing it.

 

 

 

 

[Nickfromwales]

5 hours ago, mjc55 said:

Did have a mechanical fan in our en-suite, stopped working years ago and didn't bother fixing it.