dMVHR in mid-terrace victorian renovation - trickle vents needed?

[JohnnyC]

Hi everyone,

 

I'm John. I've been reading the forum for a while, but this is my first post. We moved into our victorian mid-terrace house a couple of years ago and we are doing some renovations now (side return and loft conversion; floor plans below).

 

As part of the renovation, we are doing some work that affects ventilation (category of measure according to Appr. Doc. F volume 1 of building regs):

- Removing external chimney (major)

- Insulating a suspended ground floor (major)

- Replacing more than 30% of the total existing windows (major)

- Installing internal wall insulation to less than 50% of the external wall area (minor)

- Loft conversion (minor)

 

This is likely to result in a significant decrease of the ventilation levels in the dwelling that I am hoping to address using dMVHRs. We do not have loft or ceiling/wall space left for a central MVHR system, I'm afraid.

 

The kitchen will have an extractor fan for the cooker with air recirculation.

 

At the moment I am considering installing the following dMVHR units:

- Vent-Axia Tempra (9 l/s; 15 l/s boost; unbalanced) - loft bathroom

- Vent-Axia Tempra (9 l/s; 15 l/s boost; unbalanced) - first floor bathroom

- Vent-Axia Tempra (9 l/s; 15 l/s boost; unbalanced) - ground floor cloakroom

- TBC (any suggestions for specific models?) (~20 l/s; 60 l/s boost; unbalanced) - open plan kitchen living area on ground floor

 

These should satisfy building regulations' minimum ventilation levels for the whole dwelling in terms of:

- minimum extraction ventilation for wet rooms

- 4 rooms: 37 l/s

- total area: ~42 l/s

 

Since we are changing the windows, I am also installing background ventilators (trickle vents) as follows:

- no trickle vents in loft bathroom

- no trickle vents in first floor bathroom

- no trickle vents in ground floor

- no trickle vents in first floor front room

- trickle vents in first floor middle room

- trickle vents in first floor back room

- trickle vents in loft bedroom (velux windows and Juliet balcony)

 

I am trying to ensure that all rooms will have adequate ventilation. The windows towards the front of the house though have a particular shape that will benefit from not having trickle vents (this would be a real eyesore). So I would prefer to avoid installing these.

 

It would be great to get feedback on what people think about this and whether I should be implementing other approaches to ensure a correct level of ventilation. In particular:

 

1. Is the dMVHR in the kitchen going to be enough to provide ventilation to the whole ground floor?

 

2. Do I need to add a trickle vent to the non-bay-window in the first-floor front room? If so, what equivalent area mm2?

 

3. Any other suggestions for things that I should be considering?

 

Thanks very much in advance for the feedback.

 

Cheers,

John

 

 

 

 

 

 

[JohnMo]

Biggest trouble with dMVHR is they have a small area of influence, and do not give whole house ventilation, unless in every room space (and/or are reversing and well planned). The Tempra dMVHR isn't the most silent vent system from what I can gather. They are not really that efficient.

 

Not sure your current plan will be very good at actually giving a well ventilated house.

 

In all likelihood your bedrooms will be very stuffy and there is no ventilation, the trickle vents will do very little to help on their own. For trickle vents to be effective, they need a fan in a wet room to pull air through them.

 

I would do dMEV, something like a Greenwood dMEV fan is silent, draws next to no electric, couple that with humidity activated trickle vents, you only ventilate as required, so you are not wasting energy.

 

 

[JohnnyC]

Thanks very much for the reply. That's very helpful feedback. That's what I feared re first floor.

 

For dMEV, do you mean to have these instead the dMVHRs but in the same locations? Without heat recovery, I'm concerned that I'm going to be unhappy letting all that energy go to waste.

 

Do you have suggestions for other dMVHR units that I should look at? I have seen the BSK ZEPHYR and alike, and they are more silent, although I was not convinced that the 70 seconds on/off was something that was going to work in my case, and I assume that this won't solve the issue with ventilation on the first floor...

 

In the meantime, I'll give it another go at seeing if I would be able to fit ducts for a centralised MVHR system since we are lifting the floorboards on the first floor anyway.

 

Thanks again!

[JohnMo]

6 hours ago, JohnnyC said:

In the meantime, I'll give it another go at seeing if I would be able to fit ducts for a centralised MVHR system since we are lifting the floorboards on the first floor anyway.

 

If you are going this direction anyway look in to cascade MVHR. Units like FreshR and BluMartin use this principal.  Don't have to use those units, but the way they do it, can be done with normal MVHR units. 

 

This is how FreshR proposed we did how house.  Basic three extract points in bathrooms and 2 supply points, one in hall and one in the lounge.

 

 

 

6 hours ago, JohnnyC said:

Without heat recovery, I'm concerned that I'm going to be unhappy letting all that energy go to waste.

Some reading material comparing systems.  

 

Atamate_SDAR+Paper+2019+(1).pdf