MVHR & wet room windows… any thoughts on fixed vs opening?

[fatgus]

Does anyone with MVHR have fixed bathroom windows?
 

A couple of potential suppliers have suggested it, so we’re giving it some consideration… I’d guess MVHR negates the need to open? 🤷🏻‍♂️

 

Or would it be a daft mistake?

[JohnMo]

Think about summer cooling also, opening windows allows cross flow ventilation.

 

We mistakenly have two bedrooms without opening windows believing MVHR was the saviour for cooling blah blah. Get opening windows you can leave them shut or open if you want. Fixed are fixed closed always 

[marmic]

daft mistake!  we have a mix of fixed and opening - but every room has an opener. .  The MVHR extraction is excellent and it's never damp whatsoever but the occasional stinker might need some extra air.    In fact the bathroom window needed a rare open this morning 🤣     not experienced summer yet -  in theory we won't overheat, but if we get weeks of hot weather I think night cooling will be necessary.  Handing and positions of openers I considered carefully to maximise cross flow 

[fatgus]

2 minutes ago, JohnMo said:

Think about summer cooling also, opening windows allows cross flow ventilation.

Good point 👍👍 We’ll have plenty of opening windows for cross flow night time cooling of the bedrooms & living area in the summer, but the arrangement of the wet rooms means there would be no air flow in that area of the house, other than via the MVHR.

 

11 minutes ago, JohnMo said:

We mistakenly have two bedrooms without opening windows

 

We ( or more accurately, I ) made a similar mistake of having only french doors in our current bedroom (ground floor). Lovely view of the garden, but it’s a right pain in the summer… they’re crap doors that are either closed or flapping about in the slightest breeze. We should really put a window in…

[fatgus]

6 minutes ago, marmic said:

daft mistake!  we have a mix of fixed and opening - but every room has an opener. .  The MVHR extraction is excellent and it's never damp whatsoever but the occasional stinker might need some extra air.    In fact the bathroom window needed a rare open this morning 🤣     not experienced summer yet -  in theory we won't overheat, but if we get weeks of hot weather I think night cooling will be necessary.  Handing and positions of openers I considered carefully to maximise cross flow 

😁👍👍👍

 

Opening it is then!

 

We’re probably going for top hung, so there’s presumably not much we can do to maximise cross flow? The positions are determined by both the internal layout and my obsessive need for consistent spacing between windows 😬

[Simon R]

53 minutes ago, fatgus said:

Opening it is then!

Well, yes, but possibly no. If you have havefever, it may be worth planning in one or more small A2A units to run off solar. 

It also means the house is at a nice temperature when you come home with out having to leave windows open.  A single 3.5kWh unit keeps out 180m2 structure very comfortable.

One more thing to consider!

 

[Oz07]

Opening

[Conor]

We've four bathrooms, only one has an opener, it's never opened.

[fatgus]

26 minutes ago, Simon R said:

Well, yes, but possibly no.

😂

[fatgus]

34 minutes ago, Simon R said:

Well, yes, but possibly no. If you have havefever, it may be worth planning in one or more small A2A units to run off solar. 

It also means the house is at a nice temperature when you come home with out having to leave windows open.  A single 3.5kWh unit keeps out 180m2 structure very comfortable.

One more thing to consider!

 

We hadn’t really thought about aircon, but it’s an interesting thought. Most of our glazing and three of the four bedrooms (fourth will be largely unused) are on the north east elevation, so we shouldn’t have overheating issues in the summer and we’re hoping that slab cooling will keep it comfortable. Will look into the A2A options though…

[Dreadnaught]

Another one here. Three bedrooms have openers. Only opened for window cleaning (tilt & turn). 

 

Two bathrooms. No windows, only large (non-opening) rooflights. All fine.

[MPx]

I'd say it depends which way the windows face.  I've had plenty of bathrooms with no windows at all and there has never been an issue with any of them (albeit all have had "extractor fans" not MVHR).  Last place we had 4 bathrooms.  One totally intrernal, which was fine.  Other 3 with one fixed floor to ceiling window in each.  Two of them absolutely fine, but the heat gain through the west facing window in the summer evenings was horrendous.  I doubt just having it opening would have been the answer, I suspect an external louvre or similar was really required.  If you live in the countyside as we do, its beautiful...but if you open your windows you do invite in a lot of lodgers (particularly after dark with the lights on) and not all of them are welcome.   Opening windows other than in very controlled situations is greatly overrated in my view.  Bring on the MVHR!

[fatgus]

On 29/03/2026 at 23:02, MPx said:

I'd say it depends which way the windows face.  I've had plenty of bathrooms with no windows at all and there has never been an issue with any of them (albeit all have had "extractor fans" not MVHR).  Last place we had 4 bathrooms.  One totally intrernal, which was fine.  Other 3 with one fixed floor to ceiling window in each.  Two of them absolutely fine, but the heat gain through the west facing window in the summer evenings was horrendous.  I doubt just having it opening would have been the answer, I suspect an external louvre or similar was really required.  If you live in the countyside as we do, its beautiful...but if you open your windows you do invite in a lot of lodgers (particularly after dark with the lights on) and not all of them are welcome.   Opening windows other than in very controlled situations is greatly overrated in my view.  Bring on the MVHR!

 

Very good point. All bar one of ours are SE facing, the other is NE but will only get any sunlight in the very early morning. All quite small windows too.

 

 

[joth]

On 28/03/2026 at 09:06, fatgus said:

A couple of potential suppliers have suggested it, so we’re giving it some consideration… I’d guess MVHR negates the need to open? 🤷🏻‍♂️

 

Did they give a particular reason? Curious that a few suppliers suggested it, specifically for bathrooms. Guess because not needed for fire regs? But still curious if any reason for there aside some marginal cost-savings.

 

I'd definitely go with opening, even though we rarely use ours for cooling much as we'd like to: too much street/train noise when the windows open, plus it lets a lot more dust in. (And smoke if neighbours have the coal fire going). Obviously that's all situational.

We actually got the master ensuite with flyscreen pre-installed, thinking it would be useful for summer cooling, but in practice is still allows too much noise in but totally ineffective at cooling the bedroom. (Yet makes for an uncomfortably cold bathroom in the morning and makes the UFH in there work harder!)

So anyway yeah we never use the opening on it aside for cleaning/maintenance, but I'd still want a stronger reason for not getting it. The next owner of our house maybe German and want their Lüften ritual.

 

 

[fatgus]

50 minutes ago, joth said:

Lüften ritual.

 

I had to Google that! Not quite as exciting as I imagined 😂

 

51 minutes ago, joth said:

Did they give a particular reason?

 

Essentially to make their quotes more competitive.

 

We're sticking with opening. The saving, as you say, is pretty negligible and I just know we'd regret it at some point if we go for fixed.

 

 

[craig]

On 02/04/2026 at 15:48, fatgus said:

Essentially to make their quotes more competitive.

 

Exactly this, with MVHR there isn't really any need to have it open and actually better if it isn't because of losses in heat recovery "if" it's open to deal with steam etc. It's not just about heat recovery but also to disperse smell, someone drops one and you can't open the window, the poor bugger that goes in afterwards is going to a create a clean up in aisle one to deal with.

Edited 7 hours ago by craig

[-rick-]

39 minutes ago, craig said:

someone drops one and you can't open the window, the poor bugger that goes in afterwards is going to a create a clean up in aisle one to deal with.

 

We are such delicate flowers these days! Don't get me wrong, if I get to build I'm getting the cisterns with built in extract to remove the smells at source but to have this as a notable selling point for a £5-10k installed item makes me laugh.

[ProDave]

On 28/03/2026 at 09:21, JohnMo said:

We mistakenly have two bedrooms without opening windows believing MVHR was the saviour for cooling blah blah. Get opening windows you can leave them shut or open if you want. Fixed are fixed closed always 

How did you even get that past Building Control?   Means of escape?

[craig]

1 hour ago, -rick- said:

 

We are such delicate flowers these days! Don't get me wrong, if I get to build I'm getting the cisterns with built in extract to remove the smells at source but to have this as a notable selling point for a £5-10k installed item makes me laugh.

 

It was more tongue in cheek than anything else.

[Iceverge]

Opening. I like to towel off ina cool breeze. 

[JohnMo]

We have opening doors on to our decking in all bedrooms, but you can't really leave those open, an open window while sleeping, is very different from an open window for a sense of security.

Edited 4 hours ago by JohnMo

[fatgus]

2 hours ago, JohnMo said:

We have opening doors on to our decking in all bedrooms, but you can't really leave those open, an open window while sleeping, is very different from an open window for a sense of security.

Our current main bedroom is the same… bungalow, doors onto patio and no other windows. In the summer we often sleep with the doors open. No intruders yet, but the neighbour’s cat has joined us for the night a few times

[JohnMo]

27 minutes ago, fatgus said:

but the neighbour’s cat has joined us for the night a few times

I'm more worried about more wild stuff coming in for the night.

[fatgus]

2 minutes ago, JohnMo said:

I'm more worried about more wild stuff coming in for the night.

I imagine we have less wild beasties here than in NE Scotland… a cat’s about as dangerous as it gets here. Or maybe a rabbit…