Heat Recovery Ventilation Rertofit

jimzy

Hi all,

I built a house around 3 years ago, and due to a combination of being both eager to get into the house quickly and any really good knowledge of renewable / energy efficient methods it was built with bog standard insulation methods (fiberglass, wall vents, cavity wall, the usual irish inefficent method!). I regret it all now of course!

So now a couple of years down the line im not entirely happy with the quality of the heat in the house during the winter. (During the summer it's great, we have some great large south facing windows that give good light and heat to the house.)

In an effort to make the house more efficient I have been researching the possibility of retrofitting a HRV system. Has anyone any experience with retrofitting these systems? Will it be worth the pain and cost!? The house is a dormer, so we have easy access to crawl space throughout the house (i think this might make things slightly easier in fitting the ducting).

I also read that external insulation is one of the most efficent options in retrofitting houses. Has anyone experienced this either? Cost / Installation / Efficieny? Any help muchly appreciated!

MicktheMan

First off, tackle the easy stuff first. How much insulation is in the roof space. can this be improved on?
With a heat recovery system it is important to know how airtight your house and put the effort in to make it as airtight as possible first. Fix / seal draughty dooes/windows. If you want to know if mhrv will work (i.e. recover heat while ventilating) have an airtightness test done and if the result is below 5 m3/hr/m2 at 50Pa then your house may well benefit from MHRV. If you do go down the mhrv route, then try to have the duct runs within the thermal envelope of the house, not in a cold roof space.

External insulation is the business if applied properly. You will need to fill you cavity first as there is no point in external insulating if this is not done. Pick your installer very carefully. Being registered to a government agency is no guarantee of qaulity, expertise, experience or workmanship.

Hope this helps,
Mick

jimzy

Hi mick, thanks a lot for the advice, that really helps clear things up in my head.
Yeah it makes a lot of sense to upgrade my insulation and tackle any draughts before going ahead with a mhrv system. I'll definitely do that first, then see how things are from there.

I just presumed the ducting could just run in the attic space, and be nicely hidden out of sight! So this would need to be within the thermal envelope (I presume this is to avoid heat loss?). I'm sure that would mean a lot more work (and cost). It's not really an easy job to retro fit mhrv systems then is it?. (Either the ducts would need to be in sight or lots of flooring/plasterboard would need to be removed??)

gizmo555

jimzy wrote: »

I just presumed the ducting could just run in the attic space, and be nicely hidden out of sight! So this would need to be within the thermal envelope (I presume this is to avoid heat loss?). I'm sure that would mean a lot more work (and cost). It's not really an easy job to retro fit mhrv systems then is it?. (Either the ducts would need to be in sight or lots of flooring/plasterboard would need to be removed??)

Running the ducting within the thermal envelope is the optimal way to go, but you can run it in the attic space / crawl space, provided it is adequately insulated. I had a system retrofitted to my dormer bungalow last year and this is how we went. Where possible, ducting was covered with the fibreglass quilt insulation we were adding to the attic, and where it was exposed it is wrapped with a self-adhesive insulation - the easiest way to describe this is it looks like foil-backed bubble wrap.

jimzy

Thats great gizmo, thanks for the info. So what are your thoughts on the mhrv system then? Do you see a serious benefit from the standard ventilation of the house that was there previously? What were your costs like for retrofitting the dormer, do you mind me asking roughly ballpark?

gizmo555

Cost for my ca. 2,200 sq ft house was around €5k. About 10% of this was due to the use of fire stopping vents, which close automatically when the air temperature in the room reaches 70C. I would strongly recommend anyone considering installing HRV to read this thread on HRV and fire spread and bear in mind the good advice in it:

http://www.boards.ie/vbulletin/showthread.php?t=2055385732

Our system is a vast improvement on what was there before, a combination of hole-in-the-wall vents and trickle vents in window frames. These either didn't give enough ventilation in calm weather, or froze us when it was windy. The HRV provides a consistent level of ventilation which eliminates condensation and lingering cooking smells, without drafts. I find I sleep better - I used to be in the habit of sleeping with a window open year round, but my wife wouldn't hear of this. Mornings would find our bedroom unbearably stuffy with windows streaming condensation. Now we get the fresh air I want without the wind chill she hates! The heat recovery part of it seems to work pretty well, even in the present cold weather.

The only problem I've had so far is the condensation drain freezing in the present weather. A nuisance but not a disaster. I just disconnected the hose and placed a plastic basin under the drain. The supplier has promised to call and see can he work out a way of preventing a recurrence - mind you this is, we're told, a once in fifty years cold snap! It was -6.5C here overnight in Mayo . . .

PS, Jimzy, PM sent with details of the supplier I used.

gooner99

gizmo, can you pm me the details also.thanks

jimzy

Hey gizmo, thanks for the feedback, that really sets things right in my mind.
I think its probably the best investment for the overall level of comfort in the house. In comparison to solar panels it seems like a much more worthwhile investment to me.

Thanks for the details too gizmo, ill give those guys a shout - that price sounds very reasonable to me too.

Holla23

Hi Gizmo,

Planning to build in Mayo so can you please pm me the details also?

Thanks!

gizmo555

PM sent.

tred

Again I echo above, Get your airtightness test done, and then see can you fix the problem. The hole in the wall vents arent going to be your problem, they are easy to fix!. You will have leaks at the roof level/ Windows/Doors. A MHRV doesnt insulate your house, All that it does, is takes the wet air from all your wetrooms, and before it dumps it outside, it takes any warmth from it, and transfers it to the incoming air, with the added cost that this device uses electricity in your attic 24X7.

uptowngirly

Hi Gizmo!

Could you PM the name of your supplier too please?

oconnb3

hi gizmo, 4 yrs on how is your MVHR going, is maintenance only once a year, would you mind letting me know what is the name of the system you used

gizmo555

oconnb3 wrote: »

hi gizmo, 4 yrs on how is your MVHR going, is maintenance only once a year, would you mind letting me know what is the name of the system you used

It's working fine - once it's installed and running, you pretty much forget about it.

Maintenance amounts to cleaning the inlet and outlet filters every three months and changing the filters annually. Takes ten minutes tops. Apart from that, if I think of it, now and again I run the vacuum over the extract vents, which can tend to get a little dusty - that takes just seconds.

Have sent you a PM with the details of the maker.

oconnb3

back again Gizmo did the installer come along and design a system for your house? did they tell you where the ducts were to run, what is the airtightness of your house? we are going to strip apart the up stairs and going for a 3 ACH score

Supercell

Hi Gizmo, we are thinking of getting this because our son has asthma and apparently these type of systems give much cleaner air inside the house. Would you mind PM'ing me also the name of your supplier?