Basic component and setup Q's

[MarkyG82]

Hi all.  Been reading a load of great stuff on here and elsewhere online.  There are a few things that I cant get my head around so I'd like to ask a few Q's.  Hopefully no question is a silly question!!  I'm a DIYer by the way.  Engineer and keen woodworker so happy in my abilities.

 

1. How do you get semi-flex ducting to be square to the inlet/outlet?  Seen a few comments saying try to position the vent so the duct is straight on to it.  What about in the loft, do you have a length of duct looping up from the fittings and then routed through the roof to reduce the bend radius?  Seems prohibitive to insulating.  What about if you have the duct running horizontal along a ceiling, how do you get it to turn 90 down through a vent?

2. I'm looking at a Brookvent unit but they don't seem to get much mention on here.  Nearly 200m2 house (by the time we have extended) so looking at 200/300 m3/h flow (trickle/boost).  Happy to be pointed in the direction of a good value unit that has all the usual bells on (summer bypass, boost by humidity and switch, etc). 6 in 5 out with some doubled up depending on type/duct length.  Is there a reason not to use the Brookvent unit?

3. There also seem a mix of views on here regards use of MVHR in an older house.  Lots on here suggest anything less than Passivhaus there is no point.  I'm working on our house but it definitely wont be a Haus.

 

In the design stage right now and hoping to start putting a shopping list together soon.  Probably going for 75mm ducting due to the limits on retrofitting.

 

Comments very welcome.  

 

Thanks

Mark

[joe90]

1 hour ago, MarkyG82 said:

Hopefully no question is a silly question!! 

Definitely not, silly is not asking. Usually the outlets do the 90’ themselves, however I made my own (another avid DIYer, and tight!).

 

[MarkyG82]

@joe90 Thanks.  Love that you took the photo on the table saw too! Often the only empty surface in my garage.

[JohnMo]

You can get bends and plenums which give you direction changes.

 

Your boost only needs to be 25% above normal flow.  Your normal flow is between 0.3-05 ACH.  So work out you ventilated area of the house and divide by 2 to 3 to get your overall flow rate.  The extract and supply should be equal and be at the rate you calculate.

 

Put a manual boost switch in kitchen and outside bathrooms.

[MarkyG82]

So I'm getting more info together slowly.  I understand how the systems work now and with extension designs changing the routes for the ducting have changed a little.  As a result, I have a few more questions that general research fails to answer.

 

1. How do you seal where the ducting penetrates the ceiling? (assuming the main system is in the loft)

2. Is the air tight envelope generally the outer skin of the house?  If inner, how do you seal penetrations like plug sockets?

3. Is there a way to cleanly route a duct from vertical to horizontal without a humongous box-out?  Am I going to require a 90 bend fitting to achieve this, with a smaller box out?

4. This will probably need answering by our builder/structural eng.  If I wanted to site a outlet in a block wall high up between a door and external wall would drilling an 80mm hole reduce the integrity of the house?

 

For points 3 and 4 see the attached.  Red line is my proposed route from the cupboard space above with the cross being the outlet site.

[ProDave]

These are typical room terminals, the pipe(s) come out parallel to the ceiling

 

 

Our MVHR unit has 4 speeds available.  Slowest speed is used for normal, second fastest is used for a gentle boost while cooking, and fastest speed is used for maximum ventilation rate when showering.

 

The yellow sheet on the wall is the air tight membrane, everything is kept inside that, battens form a 25mm void for pipes and cables then plasterboard so no draughts through your light seitches.

 

How far into the build are you, if you get the chance I really really recommend making your whole roof a warm roof with insulation and air tightness following the roof line. It is SO much easier to detail.  If instead you go for a cold loft with the insulation on the ceiling you will have a LOT of detailing as much of your MVHR pipework and the MVHR unit itself will be outside the air tight envelope of the building.

[MarkyG82]

Thanks!

Should have probably mentioned it's a retrofit and we are extending.   Not started yet.  Currently getting quotes from builders.

 

The utility is the current kitchen with the current wc the other side of the wall to the location in the above plan.  All internal walls are block. 

As part of the extension we are replacing all windows and external doors.  This alone should give us much improved insulation.  I just need to figure out the fireplace as that is the final gaping hole.

Edited November 23, 2022 by MarkyG82
build times

[MarkyG82]

Holy thread resurrection batman!

 

Due to start picking up tools for the extension next month so I am picking this back up. 

A quick nose on BPC and here suggests the Vent Axia Sentinel as a good option to base the system off.  Are there any other brands or models I should be looking at?  Requirements are:

- summer bypass

- boost 

- reasonable quality

- not top end expensive

 

thanks.

[Deniance]

I’ve bought two Brookvent, the items seem ok, but they are very very expensive, replacement fans are knocking on for 300 each, sensor failed on mine and that was 50 beans, when it turned up it’s a circuit board and a 5 inch cable , looks about 99p worth, the filters are crap quality, they are stringy foam around a metal square and they start breaking as you remove them, all the green coloured 1.2 air cycles you can’t open them or service them, the aircycle 1.3 you can

 

they are helpful on the phone but won’t help with other stuff , I bought a cheap eBay 1.3 but I rang up and asked to buy the pcb to make it a digital version and they tell you it can’t be done and you have to pay best part of 2 grand for a new unit but you don’t

[MarkyG82]

So I think I've come up with an idea for the living room supply.  What are the thoughts on boxing in ducting?  The supply could run next to the chimney breast in bed3 and come out of the ceiling in front of the fireplace in the living room. 

I need to measure the wall placements but it's possible it could drop to the centre of the wall to be symmetrical.  That's a detail to figure out later.  The duct could then be boxed in as it passes thorough bed3 and it would end up looking like part of the chimney breast.  

That supply would be above the TV and opposite the sofa (TV over the fireplace).  With supplies in the hallway (by the front door) and one in the play room.  Then extracts in the kitchen and utility.  Would the supply location be acceptable?  Would we even need one in the hallway?  We are likely to be supply heavy upstairs anyway.

[MarkyG82]

For clarification here is a diagram of what I'm intending.  The duct would come down from the loft - through bed 3 - out of the ceiling in the living room above the TV.

Edited December 14, 2023 by MarkyG82

[JohnMo]

Downstairs I would do a simple cascade system.

 

Supply air only to lounge (around 50 to 70m3/h depending on floor area downstairs), use a fan in the internal wall between snug and utility. Supply air will be moved by the two MVHR extracts and via the fan in the wall of the snug, the airflow will be the blue lines on the drawing.  The fan could be a simple dMEV fan, like a Greenwood, they are almost silent and would run at min speed.

 

You also need an extract in the toilet, or you could cascade the utility into the toilet (another fan in the internal wall), as you wouldn't want smell from the toilet being pulled into the utility

 

[MarkyG82]

So the current design has a single extractor in the WC to handle that and utility. Along with an extract hood in the kitchen. Planning on leaving the kitchen hood in place as it'll only ever run for minutes at a time. Just need to make sure it has adequate flappy plate things.

The WC extractor I was going to use as the extract from the mvhr. Only thing I hadn't considered was the flow through the wall in the snug. What benefit would that bring over a supply? The airing cupboard straddles that wall below the "U" of utility. That's the route for ducts that side of the house.

[JohnMo]

10 hours ago, MarkyG82 said:

the WC extractor ...extract from the mvhr.

What do you mean?

 

10 hours ago, MarkyG82 said:

The airing cupboard straddles that wall below the "U" of utility. That's the route for ducts that side of the house.

If you have an easy route to the snug ignore my previous comments about cascade.

 

10 hours ago, MarkyG82 said:

single extractor in the WC to handle that and utility

You need to look at the airflow where the air is coming from, if you only extract from the toilet the air could just short circuit under the the utility and WC doors and miss the utility out

[MarkyG82]

4 minutes ago, JohnMo said:

What do you mean?

 

 

 

You need to look at the airflow where the air is coming from, if you only extract from the toilet the air could just short circuit under the the utility and WC doors and miss the utility out

 

The design is not based around MVHR and there is currently a plan to have a single extractor fan in the WC that is to handle both WC and utility.  I was planning on using that point as the MVHR extract for that area.  So you are saying that with MVHR I would need extracts in both WC and and utility.  I don't think this would be an issue.  Just more expensive in ducting and need to have a think about the site of the utility point.  I guess as close to the back door as possible to get the area covered by cross flow.

[JohnMo]

Confused now

1 hour ago, MarkyG82 said:

The design is not based around MVHR

 

[MarkyG82]

1 hour ago, JohnMo said:

Confused now

 

 

The extension/build design.  Not talking about the MVHR design.  Apologies if I'm confusing you.