MVHR and trickle vents and hidden costs

Saddleview

Hello all,

new build hopefully starting soon. bungalow, likely to be masonry and A2W underfloor.
I'm looking at a good quote that I've gotten for MVHR but the only problem I have is that they don't do a summer bypass on the system. (I like that they use rigid ducting which I believe is better for noise levels??)
Main Question is: I'm wondering if I got openable/closable trickle vents as part of my windows that would ventilate the house in the summer months? Or is this madness with a host of disadvantages?

I'm all on for using MVHR as we're on a high exposed site and i don't want whistling 4" vents in nearly every room but I've just been reading up on air tightness and the likelihood of 3-5k having to be spent on sealants and tapes etc. to get good airtightness.

Anyone have good experience or suggestions to what I should go with?

Thanks

BryanF

Re triple vents: yes, Madness

Best advice I can give is get everything drawn & detailed out before you start.

Calahonda52

Get a supplier that has summer bypass
trickle madness as you say.
A/T needs to be addressed in the context of what your target ACH is, especially on an exposed site.
Poor A/T on an exposed site will kill your heating.

sydthebeat

Open the windows in the summer, when needed.

Saddleview

Re opening windows : I think I understand that the MVHR system has to be left on over the summer especially for wet room ventilation. But does opening windows at this time cause the system to work too hard and other problems?

sydthebeat

Saddleview wrote: »

Re opening windows : I think I understand that the MVHR system has to be left on over the summer especially for wet room ventilation. But does opening windows at this time cause the system to work too hard and other problems?

nothing stopping you opening windows in wet rooms either... actually a better way to purge steam.

im posting on the assumption that you go for a system with no summer bypass.... while not perfect, its not the be all and end all... manual work can resolve any issues caused.

Wartburg

As the others stated before - trickle vents should be not considered. You´re buying a well insulated and tight window and than you install outdated technology to that window which makes the overall performance worse? I´ve seen so many leaking trickle vents during my AT tests and building surveys that I could fill a book with. I´m attaching just one photo to show what I´m talking about, the vent was "officially" closed during a building survey.

fatty pang

Somewhat bizarrely the draft consultation TGD-F put out last year proposes increasing the size of background (trickle) ventilators by circa 30% if relying on natural ventilation so the holes are going to get even bigger for anybody following this route if the draft remains unchanged. Unfortunately the guidance is still promoting the location of background ventilators in/on the head of window frames – Diagram 5 is unchanged.
With the ventilators supposed to be more then 1.75m above floor level (1.2.4.4) to avoid draughts, they will invariably end up in the head of the frame. Lintels being at least 2.1m and often higher the vents are invariably left open or more often, closed.

Trickle vents are not included when the window u-value is calculated, or when the airtightness and watertightness performance testing is conducted either. If they are present in the sample tested they are taped over prior to the test beginning.

Heat loss through trickle vents can sometimes be the least of the occupants problems as these windows installed in Bournemouth illustrate https://www.youtube.com/watch?v=PcmTjXk6T-Y
Like the Spencer Dock window fiasco, poor detailing and installation is the primary cause of this particular problem.

BryanF

fatty pang wrote: »

Somewhat bizarrely the draft consultation TGD-F put out last year proposes increasing the size of background (trickle) ventilators by circa 30% if relying on natural ventilation.

Can you highlight this section of the regs? is this not associated with the air change rate?

fatty pang

https://www.housing.gov.ie/sites/default/files/public-consultation/files/technical_guidance_document_f-_ventilation_2018_for_public_consultation.pdf

Page 20

1.2.4 Natural Ventilation
Ventilation Rates
1.2.4.1 Where the air permeability is 5m³/(h.m²) or greater and greater than 3m³/(h.m²) , the minimum total equivalent area of background ventilators providing general ventilation should be 30,000 42000mm² with an additional 5,000 7000mm² for each additional 10 m2floor area above the first 70m² of floor area measured…

The strikethrough is what is in the current TGD

BryanF

fatty pang wrote: »

https://www.housing.gov.ie/sites/default/files/public-consultation/files/technical_guidance_document_f-_ventilation_2018_for_public_consultation.pdf

Page 20

1.2.4 Natural Ventilation
Ventilation Rates
1.2.4.1 Where the air permeability is 5m³/(h.m²) or greater and greater than 3m³/(h.m²) , the minimum total equivalent area of background ventilators providing general ventilation should be 30,000 42000mm² with an additional 5,000 7000mm² for each additional 10 m2floor area above the first 70m² of floor area measured…

The strikethrough is what is in the current TGD

So how is it ‘bizarre’ that the Natural vent requirement has increased to allow for increased air-tightness levels?