Hoping for an answer to a potentially stupid question.

[Dazz71]

Hi everyone. 

 

So, here we go, we are in the midst of renovating a 1890s bungalow and are wanting to fit an mvhr system pretty soon.  

At the moment we've put in underfloor heating. Heatpump. Insulation etc etc.

 

My question is about the mvhr unit itself...   

Would it be a good to sit it on its own heated concrete plinth/slab in the roof?   

Or should I forget that idea and just install a loop directly in to the unit?   

Or both?   

Or neither?

 

Would it be a good idea to 'build' an insulated room around the mvhr unit itself?

 

Because of where we are at with the renovation then I can pretty add what is needed as I go along. It wouldn't take too long to add strength to the joists, add an extra heating loop to our underfloor heating manifold specifically for the mvhr unit. Good idea? Terrible idea?

 

Any insight, or other ideas are most welcome. 

 

Cheers.

[Mike]

Welcome to the forum!

 

1 hour ago, Dazz71 said:

Would it be a good idea to 'build' an insulated room around the mvhr unit itself?

If the loft is the only place it will fit, then installing it within an insulated but unheated enclosure is good. Your loft access trap also needs to be big enough to get it through, and you'll need good access for filter changes & other maintenance. And, although good MVHR units don't make much noise, I'd not put it directly over a bedroom if there was an easy alternative. If it will fit within the heated envelope - utility room, kitchen or elsewhere - then that would be preferable.

 

No need for a heating loop unless you're planning to use it to feed a duct post-heater to top-up the air supply temperature. That's not often done except when the MVHR is used as the main source of heating in Passivehaus.

 

BTW, if you've not already picked it up, add airtightness to your to-do list. It's likely to be the most cost-effective improvement you can make & it plays a major role in protecting the fabric of the building from potential moisture damage.

 

[JohnMo]

8 hours ago, Mike said:

 

BTW, if you've not already picked it up, add airtightness to your to-do list

Would add to this - if airtight isn't at the top of your list of priorities, don't bother with MVHR. Look at demand control dMEV or MEV instead.

 

No need to add heating to the MVHR unit, a good unit is a big block of insulation. Outside the heated environment all your ducts need good insulation and vapour protection to stop condensation.

 

In a loft you need access ladder, access walkway and a maintenance area all as proper flooring. Or better still don't put it it up there.

[Dazz71]

9 hours ago, Mike said:

Welcome to the forum!
 

 

Hi.

Thanks for the welcome and reply.

 

Location:

It probably isn't the only place it can go. I just figured it'd be the easier to route the ducting. I've never even considered about other places. Thank you, I'llb look for other places it can go. 

 

Passiv/Top up heating:  

Yep, the idea for the extra heating loop was to help the incoming air be the same or higher than what's already in the house. The reason behind this is mainly because my wife seemingly feels every draught within a 75 mile area!!  

So if I can get the incoming air higher than the room temps it'll be much better for me. 

 

Air tightness:  

It is a concern with everything we've done so far. We've ripped out old rotten floors and insulated and sealed as possible. Taped the joints. Same goes with the roof that we've renovated so far. It won't ever be near passivhaus standard though.

[markc]

@Dazz71, hi and welcome, we have an 80’s bungalow with decent insulation but quite draughty and we often leave the door/s open so Air tightness and MVHR doesn’t make much sense, but earlier this year we had 3x A2A heat pumps installed and they have made a massive difference. Blown warm air goes down well with my wife and the added bonus of air con has been great, plus running costs have been surprisingly low especially as there’s only the two of us so heating and cooling the whole place isn’t necessary.

[Mike]

4 hours ago, Dazz71 said:

the idea for the extra heating loop was to help the incoming air be the same or higher than what's already in the house. The reason behind this is mainly because my wife seemingly feels every draught within a 75 mile area!!

I'd only consider adding a pre-heater if choosing a vent style that discharges downwards and if I didn't have the space to site them away from sensitive areas - beds, seating and the like; the supply air can be noticeable and, in cold weather, can be a couple of °C cooler than the general room temperature. However, if you use ceiling mounted vents that use the Coanda Effect - for example Zehnder Luna - the supply air will be dispersed at ceiling level and, provided the minimum distance to the walls is respected, there will be no problem.

 

[Dazz71]

8 hours ago, JohnMo said:

Would add to this...

Hi and thanks for the info. 

 

I have looked at other types of ventilation but it will have to be somewhat heated due to the wife not liking draughts. 

 

Air tightness is something we are going for, but it's a work in process type thing. Once everything is done then the place will be quite air tight.

 

When you say vapour protection what do you mean? I was going to use insulated ducting, would I need to do anything extra?

 

Cheers.

[Dazz71]

5 hours ago, markc said:

@Dazz71, hi and welcome

Hi, thank you. 

 

We have already got a heatpump and underfloor heating. Do you think an a2a would be better than mvhr?

[Dazz71]

1 hour ago, Mike said:

  Coanda Effect

 

 

All vents will be in the ceiling.

 

Only one vent will be near a seating area and that one is in the living room. The rest will be as far away from beds etc as possible.

 

You mention coanda effect. I take it general vents are just going to push the air out in a specific direction?

 

Cheers.

Edited 1 hour ago by Dazz71

[JohnMo]

1 hour ago, Dazz71 said:

When you say vapour protection what do you mean? I was going to use insulated ducting, would I need to do anything extra

You should be covered - but be careful with your choice here as not all the same from a pressure drop perspective

[JohnMo]

1 hour ago, Dazz71 said:

 

All vents will be in the ceiling.

 

Only one vent will be near a seating area and that one is in the living room. The rest will be as far away from beds etc as possible.

 

You mention coanda effect. I take it general vents are just going to push the air out in a specific direction?

 

Cheers.

Normal nozzle or vent are different from coanda effect. The coanda ones are specifically designed to encourage air flow to follow the ceiling, ours travel around 6m before coming downwards. By that time the air is at ceiling temperature - you will never feel a draft - ever. It also allows to use way less duct and have supply points near doors etc, and air moves across the room before coming down and being swept across the room back to an extract point