Opinions on suitable retrofit ventilation for existing house and extension

batman1

We are at the initial planning stage of our modest rear extension and renovation with our chosen architect and have been looking at improving the ventilation in the whole house as part of the job.

It is a 2002 built dormer semi d and was extremely cold and draughty up until last year when we got walls and attic spaces insulated as best we could. This was a huge improvement in the house. It was a long term project to do the extension etc and part of the plan was to eventually improve ventilation after doing the insulating job as we don't want to end up with condensation issues.
On cold days we would get a small amount of condensation on the windows in the morning.

The RH in the house is generally between 55-60% at a temp of between 18 - 21 C when the heating is on etc.

As it stands, none of the rooms have wall vents except for extractor fans in 2 bathrooms (which, on a windy day cold air comes in even if they are on!) The existing windows have trickle vents.

We are hoping to replace the windows to more efficient ones as part of the refurb.

Our arch says MHVR won't work in our house and is more suited to airtight dwellings and would be expensive to retrofit anyway. He has suggested perhaps positive ventilation or extraction with suitable wall vents.

I would like to hear any opinions on options we might have as to best improve the overall ventilation without having draughts cooling the house down too much as happens when opening windows each morning.

1. Is it worth the expense to replace the double glazed PVC to a more efficient double glazed or triple glazed type and have them sealed and insulated around the frames properly?

2. Is a positive ventilation system an option and is it any good?

3. What other options could we consider for improving general ventilation.

MicktheMan

batman1 wrote: »

1. Is it worth the expense to replace the double glazed PVC to a more efficient double glazed or triple glazed type and have them sealed and insulated around the frames properly?

2. Is a positive ventilation system an option and is it any good?

3. What other options could we consider for improving general ventilation.

1. It depends really on current state of the windows and the extent of the leakage between the frames and the walls. Good tg units will also add to comfort because the internal glazing temp will be warmer than what you have now.

2. I prefer an MEV system (mechanical extraction ventilation) over PIV.

3. Have you researched DCV (demand control ventilation)?

PROJECT K

+1 on Micks response, look into DCV with humidity control trickle vents in windows or wall - next step up would be a decentralised heat recovery system where you have effectively a HRV unit in each habitable room (expensive for the top of the range system but you can mix and match with humidity control units/HRV subject to suppliers design). Google Lunos or search on you tube and it will explain it much better...!

Either way it would be very worthwhile to see how you can best seal the house up first, simple unobtrusive measures on a leaky building can yield great results...

good luck with the project!

PK

batman1

MicktheMan wrote: »

1. It depends really on current state of the windows and the extent of the leakage between the frames and the walls. Good tg units will also add to comfort because the internal glazing temp will be warmer than what you have now.

2. I prefer an MEV system (mechanical extraction ventilation) over PIV.

3. Have you researched DCV (demand control ventilation)?

The current windows are cheap and nasty and although the house has become much more comfortable, sitting by a window is not pleasant. One window actually rattles in the wall if I shake it! Ideally I would like to replace them.

I haven't looked at dcv. From a brief read would I be right in saying each room gets a vent, each bathroom and kitchen gets an extractor which are all ducted to a central unit. Sensors in each room switch the system on and off depending on rh, therefore causing a negative pressure inside the house causing outside air to flow through the wall vents in each room?
Would such a system cool the house or is it subtle/in the background?

MicktheMan

batman1 wrote: »

I haven't looked at dcv. From a brief read would I be right in saying each room gets a vent, each bathroom and kitchen gets an extractor which are all ducted to a central unit. Sensors in each room switch the system on and off depending on rh, therefore causing a negative pressure inside the house causing outside air to flow through the wall vents in each room?
Would such a system cool the house or is it subtle/in the background?

Pretty much that's it.
Each room vent has a valve which opens/closes depending on the rh. The central extract fan runs continually in the background and then steps up a gear when needed (high rh).
This is background ventilation and should not cool the house.

PROJECT K

Wet rooms/Kitchens/utilities get extracts (with or without heat recovery but obviously better with HR) and habitable rooms get either humidity controlled inlets (usually incorporating nylon strip which responds to elevated humidity levels) or individual HRV fans. ventilation rate is very subtle so you wont feel any drafts. for a retrofit, unless you are undertaking a major overhaul, ducted ventilation is not going to be feasible - the two systems mentioned are not ducted to a central unit.

All ventilation will cool the house to some extent, less with HRV, but ventilation and air quality are essential (much more important than saving a few euros on heating!)

batman1

When we upgraded the insulation we done as best we could with airtightness without major work. However the main area for heat loss now seems to be the windows/doors. Our arch says the condensation now on the windows is because the walls and roof are much better than they were and the windows are now the weakest part from a thermal point of view.
There was never condensation on the windows prior to our insulation upgrade.

I suppose I would like to have a decent ventilation solution that's not just putting 4 inch holes in each room and putting a grille over them. From past experience they can be cold, draughty buggers!

There must be a good solution that could be retrofitted without major structural upheaval so that were not having to open windows to ventilated and losing loads of heat in the process.

For example if I open the windows in the morning at this time of year the temp will drop from 21 to 13 in a half hour. We then close up windows and heat the whole thing back up again.

Ush1

batman1 wrote: »

When we upgraded the insulation we done as best we could with airtightness without major work. However the main area for heat loss now seems to be the windows/doors. Our arch says the condensation now on the windows is because the walls and roof are much better than they were and the windows are now the weakest part from a thermal point of view.
There was never condensation on the windows prior to our insulation upgrade.

I suppose I would like to have a decent ventilation solution that's not just putting 4 inch holes in each room and putting a grille over them. From past experience they can be cold, draughty buggers!

There must be a good solution that could be retrofitted without major structural upheaval so that were not having to open windows to ventilated and losing loads of heat in the process.

For example if I open the windows in the morning at this time of year the temp will drop from 21 to 13 in a half hour. We then close up windows and heat the whole thing back up again.

Project K just described the solution to you.

The Lunos units don't needed major structural work just essentially a hole in the wall that covers over automatically when not needed(demand controlled).

batman1

Ush1 wrote: »

Project K just described the solution to you.

The Lunos units don't needed major structural work just essentially a hole in the wall that covers over automatically when not needed(demand controlled).

In such a system it's my understanding that the wet rooms have extraction back to a central unit and the dry rooms have the automatic wall vents which open and close as required. We hope to replace flooring upstairs so fitting extraction to the kitchen and downstairs en suite may not be too intrusive and the attic is above the upstairs bathroom.
Would anyone have an idea on a ballpark figure to install such a system into an existing house?

batman1

One thing that may put a spanner in the works is that there is a small insert stove fitted in the living room. Would this affect it enough to not be able to fit such a system?

PROJECT K

you can have extracts ducted to a central location if you wish, but my experience with this type of retrofit ventilation is that the decentralised option is best - no ducts, cheaper, less intrusive, easier to install, easier to maintain, easier to upgrade later...

any decent MHRV system whether centralised or not is expensive but with decentralised you have a series of options which have a direct impact on cost. the units can cost up to €500 each (with heat recovery) and typically around half of that for just humidity control. You should speak to a few of the system suppliers who will provide a free design and quote to suit your particular situation and take it from there...

batman1

Many thanks for the info. I would be grateful if you could name reputable companies I could contact, or pm if you cannot name them here.

BryanF

batman1 wrote: »

pm

thanks

greenfit

Hi Batman1.
Thanks for posting. It would be great if you could let us know what you decide on and would be even better to find out how the installed system performs. I feel that the industry is struggling a little to provide good (i.e. efficient and economical) ventilation solutions for retrofits
Cheers

Turbinehead

Hi guys. First time posting. I am currently doing a renovation extension job in Donegal and am looking at the lunos system for hrv. It is working out slightly more expensive than all my quotes for a centralised system but it would probably save money as I cannot really afford to drop ceiling level enough to have ducts inside Airtightness membrane which means running ducts in attic and coming through membrane in each room and trying to deal around again. Plus with centralised system I will have to build insulated room in attic.
So I would love to hear from anyone who has used or experience with lunos or similar de-centralised hrv systems. My house is a bungalow approx 1600s/ft