Installing MVHR after renovating

[avajamesbee]

Hi there,

 

We recently moved into an 80s new build house. It retains heat very well, however the ventilation is absolutely horrible - the house traps all smells. We open up all the windows and doors each morning to bring fresh air in, however this only lasts for a few hours before the air gets stale again, and it makes the house freezing. Coming from a well ventilated flat with an MVHR, this situation is driving me crazy.

 

However, we already renovated the house before moving in. We had to really, as we discovered all the ceilings have asbestos, so we had them removed and completely redone (new insulation, boarding and plastering). We then installed new laminate flooring throughout. My point is - we've just renovated the whole property, and particularly the areas where an MVHR is installed.

 

And here comes my question - is it at all possible to install an MVHR without it being very disruptive? The attic itself is not boarded up for example, and I was wondering if it's possible to run the pipes through the corners of the upstairs bedrooms or something.

 

Thanks in advance!

[Marvin]

Having installed my own here's my plan. results good.

 

 

Red= obstructions in roof space

Green= air in

Blue = air out

HRX2 MVHR unit.

 

The idea is to add air in all dry rooms and take out in all wet rooms, so smells and moisture hopefully go out the vent and are not dragged across the building.  So from this principle you should be able to work out what you need. However, a house will need downstairs inlet/outlet vents.... unless someone knows better (not impossible).

 

Hope this helps. Good luck.

 

Marvin

[avajamesbee]

Thanks very much for this Marvin. Do your pipes go through the floors/beneath the floorboards?

[Olf]

6 hours ago, avajamesbee said:

is it at all possible to install an MVHR without it being very disruptive? The attic itself is not boarded up for example

Last time I did the upstairs (3 bedrooms + bathroom + en-suite) via the attic, but downstairs only extraction from cloakroom and supply to the corner of the living room, as it was 2 meters away along the joists. Disruption: ceiling in the cloakroom (80cm wide) and boxing in the bathroom. 

The difference was remarkable, especially removing steam from the bathrooms after shower (boost by built-in humidity sensor). As it was 'botched' job from the start I used a cheap unit and branched PVC ducting to keep the cost down.

 

 

 

[Marvin]

5 hours ago, avajamesbee said:

Thanks very much for this Marvin. Do your pipes go through the floors/beneath the floorboards?

 This is our bungalow and the plan shows the layout in my loft so I just cut through the ceiling where necessary.

 

It can be very difficult to run pipes in between upstairs joists because of the services already there. If I had to retro install an MVHR system to a recently sorted house I would run pipes across the loft until they met the corner of an upstairs room and run the pipes down the room corner to the upstairs joists. But I think it could be a hell of a tricky game trying to find a route for the pipes - they are quite large - even as rectangular ones.

 

7 hours ago, avajamesbee said:

is it at all possible to install an MVHR without it being very disruptive?

So to answer your original question I think it would be very disruptive, frustrating when you find routes blocked by pipes and cables, time consuming and I wouldn't even attempt it without an endoscope inspection camera. But boldly go where other people...

 

https://acarchitects.biz/self-build-blog-mvhr-systems/

 

And finally it depends what causing the build-up of all smells. Consider the following:

 

Double glazed upvc windows don't let the air through and so should have trickle vents in them if there is no MVHR (generally) FENSA requirement

All toilets, bathrooms and kitchens should have extractor fans or openable windows. Building Regulations requirement

When I had a house without MVHR I used humidity controlled extractor fans with automatic shutters to avoid cold air coming back in even though I had openable windows. I installed them as high as I could (following manufacturers instructions either walls or ceilings) to remove the hottest, wettest and usually smelliest air first. Marvin's Requirement! ?

 

Good luck

 

Marvin

[avajamesbee]

Thanks very much for your thorough responses!!

[Oz07]

@Marvin how do you get on with that unit. I've got the same. Recently cleaned the pre filters and was impressed at what they caught but it has been dry. It seems the unit is sealed and there is no way to change the actual filters. 

[Marvin]

I purchased and installed a Polypipe Silavent Green Line HRX2 

 

https://www.polypipe.com/sites/default/files/HRX2_MVHR_Technical_Data_Sheet.pdf

 

with a summer bypass and I put all sorts of bespoke controls on it. It now looks like the name changed to the Domus HRX2-D heat recovery unit. The model is suitable for up to 275m2 floor area but I only have 106. I was careful to follow the recommended duct sizes and insulated the lot and in my small loft it was a pain in the     . 

 

It runs at 20 watts on normal and has been excellent. We can just about hear it on boost. I clean the filters once a year. My filters are a different shape to Oz07's.

 

We have had no mould issues however the 3 things I aim to improve are:

Sound travelling down ducting from one room to another.

Hot cooking smells cooling and travelling around the building

"Wet rooms" smell removal.

 

I am considering various options but any thoughts would be appreciated.

 

I have only just realised that the summer by pass is the wrong name for the facility as when it is hot outside and cold inside it actually cools the fresh air when I use the heat exchanger!  ? But I'm sure everybody else knows this.

[JFDIY]

What about the individual units that can be fitted in each room with just a hole cored through the wall.

 

Can't remember the detail, but there are someone that will wirelessly talk to each other, presumably can be configured as supply or extract as required.

 

There are also some room only units which inhale and exhale through a heat exchanger so change the air in the room where fitted more than the whole house as it were