Suggested HRV Pipe Layout??

yellatdave

Doing a retrofit on my 100m2 semi-d, upgrading my insulation & making the house more airtight. As part of this, I want to install a mechanical heat recovery ventilation system, and as money is tight, I'm going to have to do the install myself... (PANIC!!)

(1). Just wondered if the attached pic I made out is the right way to lay out the ductwork?
(2). Also, can anyone recommend an efficient (yet not too dear) HRV unit for this sized house?

Any input greatly appreciated!!

sinnerboy

Place the HRV unit in the center of the attic void i.e where the "L shaped bend into en suite" arrow is pointing and locate all inlets/outlets over doorways ( not over bedheads ! ) By doing so you will keep duct runs to a minimum - very important in terms of efficiency of the system. Not too mention less materails to buy and install

Remember the HRV has to be accessed often to change filters and it will have a condensate run off drain. Don't " shove it away" somewhere. It will control the air you breathe so don't treat like a stranger. Get to know the little noises it makes and if it makes an odd sound - investigate that blocked filter or faulty fan quickly.

Co link the fan motor to your fire alarm so it stops operating in case of fire. Only use slam shut metal fire resisting ceiling inlets/outlets.

sas

sinnerboy wrote: »

... locate all inlets/outlets over doorways ( not over bedheads ! )

I'm told that Extract\Inlet are supposed to be as far from the door as possible to avoid short circuiting the room.

My house was certainly designed to this principle.

Andrew_Doran

I installed an MVHR system in my own home last year. It is slightly smaller than yours.

I chose spiral steel ductwork (limited fire safety, healthy, and cheap) and fused fire rated terminals as mentioned by sinnerboy. Although, you may have a job finding fused supply diffusers, I did.

The unit I have is 93% efficient and is British-made, and has a humidity sensor and summer bypass. I got MVHR unit, all ductwork etc. for somewhere around €2500 from a large air conditioning supplier. The MVHR unit came in at 2/3 of the cheapest price I could find anywhere else. I'll PM you with further details.

My experience was that with no labour costs and no time pressure it was an opportunity to do a top-quality install for not much money.

General practice seems to be to put supply and extract terminals as far away from the door as possible to create cross flow, but conversely not too close to walls as it will cause down-draughts. Doors may need a slight undercut. Mine have about a 5mm gap.

To give you an idea here is a list of some of the things I bought and fitted:

- digital anemometer for balancing system, courtesy of eBay.
- galvanised steel spiral ducting, cut with angle grinder and deburr with file.
- steel diffusers & fire rated/fused extract valves.
- many fittings for same, including tees, couplings, bends, external grille, chinaman's hats for roof, etc.
- double walled flexible ducting.
- 10sq earth cable & labelled clamps for bonding steel ductwork back to main earth terminal.
- water based duct sealant, 75mm aluminium tape, MS-polymer based sealant for misc sealing, e.g. air terminal collar to ceiling.
- self tapping ductwork screws, wood screws, galvanised steel strapping, wooden battons, pop rivets for fixing air terminal collars.
- duct insulation
- pipework for 3/4" condensate drain, including soldered up u-bend trap & insulation.

sinnerboy

Short circuiting will occur where supply and extract ceiling terminals are located too close together. So in the case of the Bathroom and Bedroom 1 I may well leave the Bathroom outlet as drawn

But otherwise .....

yellatdave

Thanks for all the feedback folks...

Some great points, so changed the layout to:
(1). center the HRV system in the attic void in order to shorten pipe runs
(2). show the current orientation of the beds, etc.
(3). move supply/extract vents away from bedheads, doors & walls (within reason) to avoid draughts & short-circuiting.

Andrew, if you could PM me the details of where you got your MVHR system & galvanised steel spiral ducting, that'd be fantastic. Sounds like a great job, although your list sounds scary!!

Andrew_Doran

Something to consider: to get the manufacturer's quoted efficiency then you may or may not need additional insulation around the MVHR unit if it's located in an unheated space. Also don't forget that there will need to be a pipe run for the condensate drain with a shallow fall on it.

yellatdave wrote: »

Andrew, if you could PM me the details of where you got your MVHR system & galvanised steel spiral ducting, that'd be fantastic. Sounds like a great job, although your list sounds scary!!

PM sent. If anyone else wants a copy please PM me directly.

hexosan

This is slightly off topic but something I've wondered about MVHR, if in a rural setting and farmers are spreading silage how would a system handle this. Could the smell be circulated through the house. Or is it possible to fix something like a charcoal filter on the inlet pipe.

sas

hexosan wrote: »

This is slightly off topic but something I've wondered about MVHR, if in a rural setting and farmers are spreading silage how would a system handle this. Could the smell be circulated through the house. Or is it possible to fix something like a charcoal filter on the inlet pipe.

I can only speak for the system that I have. They do sell specific filters for removing smells. I've no idea how effective they are.

I live rurally and silage smells etc. haven't been a problem. We're from the town ( less than 1 year in the country) so we would be sensitive to smells etc.

yellatdave

Thanks Andrew for that PM, really saved me a lot of head-scratching!!

Anyway, think I've simplified it again (see blue boxes below). Would this work?
Also, was wondering if warm air supply vents should be located closer to the floor (around radiator height) while stale air extractors stay in the ceiling. Wouldn't this aid additional cross-flow?

feelinfoul

would it be worth your while taking an extract from your hot press?

jakko86

Hi guys dont mean to drag this off topic but have ye any tips or things i should do while blocklaying or joisting is in progress for the hrv or is pipe layouts etc easily sorted after. its all timber joisting 9 by 2?

BryanF

jakko86 wrote: »

Hi guys dont mean to drag this off topic but have ye any tips or things i should do while blocklaying or joisting is in progress for the hrv or is pipe layouts etc easily sorted after. its all timber joisting 9 by 2?

You require carefully coordination by arch and hrv specialist or you might end with unsightly bulkheads around your house. This is among other things is why archs seek the 'big bucks' at detailed design stage

yellatdave

feelinfoul wrote: »

would it be worth your while taking an extract from your hot press?

Thought about using that as an extra heat source, but piping would either have to be fed into 'living area' of attic conversion or fed between the small gap of floating attic floor & 1st floor ceiling, both of which I want to avoid for the extra hassle that it would entail. Instead, going to tweak layout to also extract warm air from converted attic.

jakko86 wrote: »

Hi guys dont mean to drag this off topic but have ye any tips or things i should do while blocklaying or joisting is in progress for the hrv or is pipe layouts etc easily sorted after. its all timber joisting 9 by 2?

PM me your email address Jakko & I can forward useful docs I have come across. Maybe something in there that may help.

yellatdave

Sorry for delay jakko86. Email sent.

Kitecrazy

Hi all,

Apologies if this question has already been addressed. If I install a heat recovery systems and have unused rooms; can I inhibit these from receiving warmed air, or at least reduce the flow to these rooms?
I suppose if we are heating far more of the house than necessary then this reduces the benefit of the system!

ecowise

Room supply and extract valves can be closed if desired. This applies to the circular type where the centre piece can be rotated to close it or open it by degrees. I don't know about grill type valves but presumably they have an equivalent mechanism.

sydthebeat

Kitecrazy wrote: »

Hi all,

Apologies if this question has already been addressed. If I install a heat recovery systems and have unused rooms; can I inhibit these from receiving warmed air, or at least reduce the flow to these rooms?
I suppose if we are heating far more of the house than necessary then this reduces the benefit of the system!

do you intend heating the unused rooms ie will they be heated by rads / UFH.

Kitecrazy

My intention would be to leave the radiators off when the rooms are not in use. My concern was that the MVHR would redistribute the heat to these rooms although not required.

MicktheMan

Kitecrazy wrote: »

My intention would be to leave the radiators off when the rooms are not in use. My concern was that the MVHR would redistribute the heat to these rooms although not required.

That would be the least of my concerns!

I would be more concerned with introducing a real risk of damp and mould into the unheated part of the house due to the temperature difference between heated/unheated parts.
An example:
Suppose the heated portion of the house is at 20 degC and 55%RH and the unheated part is at 15 degC and vents closed. This would mean that the %RH will be at approx. 75% in the unheated/unvented space. 75% RH over any length of time will give rise to damp/mould.