Preventing draughts?

[puntloos]

So, in a Passivhaus, the draughts from outside are not a thing, but what about air conditioning? If I have a ceiling vent, is there some way to prevent the air to be very cold near the exit of that vent? Draughts?

 

I'm thinking maybe linear diffusers are better? 

[Nickfromwales]

51 minutes ago, puntloos said:

So, in a Passivhaus, the draughts from outside are not a thing, but what about air conditioning? If I have a ceiling vent, is there some way to prevent the air to be very cold near the exit of that vent? Draughts?

 

I'm thinking maybe linear diffusers are better? 

If you want AC in an airtight house ( as I am currently installing for one of my ( PH+ ) clients ) then you do NOT make any holes to atmosphere. I chose a split AC system with a compact external unit, F-gas lines through the house, and a fixed internal unit to heat / cool that is room-sealed ( with a condensate drain ).

[puntloos]

3 hours ago, Nickfromwales said:

If you want AC in an airtight house ( as I am currently installing for one of my ( PH+ ) clients ) then you do NOT make any holes to atmosphere.

Yes absolutely, that's what I was trying to say. So there's no issue with a draught to the outside. 

 

My concern is if the AC comes from one smallish (10cm?) hole in a room, will the airflow be so high that the cold air is noticeable? 

3 hours ago, Nickfromwales said:

I chose a split AC system with a compact external unit, F-gas lines through the house, and a fixed internal unit to heat / cool that is room-sealed ( with a condensate drain ).

And separately you have a A2W (monobloc style, perhaps?) device for UFH and DHW? 

A little off-topic but I'd love to understand the brands and configuration you chose. 

 

I'm currently debating if I should go all water-based (for FCUs as well as UFH) or if I should do two units (one "AC" one "warm water" device)

[JohnMo]

Why not do UFH heating and UFH cooling? No drafts. All done from A2W.

 

Run the cooling at a fixed temp say 18 deg, there should be a decent floor cooling effect, without and condensation issues 

[joth]

5 hours ago, puntloos said:

Yes absolutely, that's what I was trying to say. So there's no issue with a draught to the outside. 

 

My concern is if the AC comes from one smallish (10cm?) hole in a room, will the airflow be so high that the cold air is noticeable? 

...

 

The essence of your question is "what size ducts, plenums and vents do I need" and the answer is "it depends on the size of the FCU and the air speed".

 

The issue is less about draughts and more about noise and having a functional system.

 

A PAW-FC-D15-1 fan coil has an outlet 570x220 (0.125m2) and shifts about 260 m3/h, so the air is moving at about 2 km/h when its on full speed. Put that through a 10cm pipe and outlet (0.007 m2) and it will have to go 33km/h or 15x the air speed as it does at the FCU outlet. That's going to be noisy and throttle the output considerably.

 

But if you use 250mm pipe and a 500x100mm linear outlet (0.05m2) that's "only" 2.5x smaller than the fancoil outlet size so airspeed 5km/h is within ballpark of working ok. 

 

(Learnt this the hardway. On that FCU I originally used a 125mm outlet and it was pants. I now have 250mm ducts into a 200x1000 linear diffuser and it's great).

 

I don't think linear diffusers are intrinsically less draughty it's just they can cover a larger area without being dog ugly. A 250mm circular outlet vent looks like a 1980s office. (A linear diffuser looks like a 2010s office)

 

 

 

 

Edited April 19, 2023 by joth

[puntloos]

8 hours ago, joth said:

 

The essence of your question is "what size ducts, plenums and vents do I need" and the answer is "it depends on the size of the FCU and the air speed".

 

The issue is less about draughts and more about noise and having a functional system.

 

A PAW-FC-D15-1 fan coil has an outlet 570x220 (0.125m2) and shifts about 260 m3/h, so the air is moving at about 2 km/h when its on full speed. Put that through a 10cm pipe and outlet (0.007 m2) and it will have to go 33km/h or 15x the air speed as it does at the FCU outlet. That's going to be noisy and throttle the output considerably.

 

But if you use 250mm pipe and a 500x100mm linear outlet (0.05m2) that's "only" 2.5x smaller than the fancoil outlet size so airspeed 5km/h is within ballpark of working ok. 

 

(Learnt this the hardway. On that FCU I originally used a 125mm outlet and it was pants. I now have 250mm ducts into a 200x1000 linear diffuser and it's great).

 

I don't think linear diffusers are intrinsically less draughty it's just they can cover a larger area without being dog ugly. A 250mm circular outlet vent looks like a 1980s office. (A linear diffuser looks like a 2010s office)

OK so a spot vent is 1980, a line vent is 2010, so with a square vent I'm good until 2040?

 

But yes, I guess the pinch point is the thing that makes noise, usually the pipe itself, the fact that you have a huge wide mouth attached to it might make less of a difference.

[Nickfromwales]

11 hours ago, JohnMo said:

No drafts.

Ok, lets get down to the real crux of this issue.....

 

My bloody spell checker says draughts, not drafts. Now my brain refuses to tell me which one is right. 

 

 

Cutting out draughts from older homes

Energy Saving Trust

https://energysavingtrust.org.uk › Blog

 

 

 

11 Jan 2022 — Draughts come into your house through gaps and cracks. First, look for any obvious gaps – visible light under and around doors and windows is a ...

 

 

Now that's from the EST, and that's how they spelt it. 

 

SO! Lets have this out before we go any further plz. I need to know.  

 

 

Loads online saying "draft", I just can't cope with this dilemma  

[Jilly]

 

The Oxford Dictionary advises: “Do not confuse draft with draught. Draft means 'a first version of a piece of writing' or 'make a first version of a piece of writing' (I drafted a letter of complaint), whereas draught chiefly means 'a current of air' (heavy curtains cut out draughts).”8 Apr 2011

[Nickfromwales]

59 minutes ago, Jilly said:

 

The Oxford Dictionary advises: “Do not confuse draft with draught. Draft means 'a first version of a piece of writing' or 'make a first version of a piece of writing' (I drafted a letter of complaint), whereas draught chiefly means 'a current of air' (heavy curtains cut out draughts).”8 Apr 2011

You know when you've said or written a word too many times and you forget how to spell it, well that was me. Done. Head fried.  

I've looked back at previous posts I've made, and I have changed to draft, instead of writing draught. Spell check / predictive text is undoing all that my teachers installed.

 

OK, all sorted. Back to the thread please!!  

[joth]

15 hours ago, puntloos said:

OK so a spot vent is 1980, a line vent is 2010, so with a square vent I'm good until 2040?

 

But yes, I guess the pinch point is the thing that makes noise, usually the pipe itself, the fact that you have a huge wide mouth attached to it might make less of a difference.

Well the thing about linear is you can make them arbitrarily large without taking up more visual clutter. They just look like a shadow gap detail all around the edge of the room. 

[Nickfromwales]

15 hours ago, joth said:

Well the thing about linear is you can make them arbitrarily large without taking up more visual clutter

The linear ones look a million dollars imo.  I've only seen these recently, not sure why, but I'm now specifying them for a lot of clients, particularly where there is a more contemporary "sharp" feel to the room / space.

I have always thought the generic valves look outdated and utilitarian, so these are the next best thing afaic. A bit more work, but I think they're well worth the effort.

[puntloos]

12 minutes ago, Nickfromwales said:

The linear ones look a million dollars imo.  I've only seen these recently, not sure why, but I'm now specifying them for a lot of clients, particularly where there is a more contemporary "sharp" feel to the room / space.

I have always thought the generic valves look outdated and utilitarian, so these are the next best thing afaic. A bit more work, but I think they're well worth the effort.

Do you have any pictures on how these look?

I will likely have a "pelmet style" (coffered ceiling) lighting setup in these rooms and I'm wondering if I can integrate linear air strips in there.. how would that be designed?

[Nickfromwales]

On 19/04/2023 at 03:04, puntloos said:

A little off-topic but I'd love to understand the brands and configuration you chose. 

( TBD ) A2W ASHP for the swimming pool and pool hall space heating. A2W ASHP ( Stiebel Eltron ) for domestic space heating and cooling ( via slab plus Brink Air Comfort AHU ) and a Mitsubishi split A/C for the 2nd storey ‘studio’ room. 
👍

[joth]

12 hours ago, puntloos said:

Do you have any pictures on how these look?

I will likely have a "pelmet style" (coffered ceiling) lighting setup in these rooms and I'm wondering if I can integrate linear air strips in there.. how would that be designed?

 

Some inspiration here

https://www.google.com/amp/s/blog.inviair.com/blog/linear-diffusers-why-are-they-so-popular%3fhs_amp=true

 

With coffered ceiling it'd be more usual to put the outlet linear diffuser in the underside of the dropped section. 

Maybe possible to have a gap above the lighting detail to allow easy air return path to the ceiling void and back to FCU.

Also, somewhere to hide the FCU service hatch? 

 

 

[joth]

Some more

 

https://images.app.goo.gl/ouz15L7kAKdhHbQr5

 

https://images.app.goo.gl/ihJT7GnGmbvFhNdd7

 

https://images.app.goo.gl/in2nZx6jenNkd3uB8

 

https://images.app.goo.gl/Jsqm7ZP3N7nYq5Wq7

[puntloos]

2 hours ago, Nickfromwales said:

( TBD ) A2W ASHP for the swimming pool and pool hall space heating. A2W ASHP ( Stiebel Eltron ) for domestic space heating and cooling ( via slab plus Brink Air Comfort AHU ) and a Mitsubishi split A/C for the 2nd storey ‘studio’ room. 
👍

Why using different brands for different things? Isn't there one "best" (for your purposes, of course) brand? 

[Nickfromwales]

7 hours ago, puntloos said:

Why using different brands for different things? Isn't there one "best" (for your purposes, of course) brand? 

For the domestic heating and cooling I chose Stiebel as it shows a COP of 6 by design, for this particular uber-low temp dwelling. 
Stiebel don’t ( iirc ) do an AC unit. 
The pool just needs a ‘dumb’ ASHP so I will choose accordingly based on service / reliability / longevity.

I chose ( will finalise my choice ) for the units based on merit / suitability and what will serve my clients the best. 

[puntloos]

4 hours ago, Nickfromwales said:

For the domestic heating and cooling I chose Stiebel as it shows a COP of 6 by design, for this particular uber-low temp dwelling. 
Stiebel don’t ( iirc ) do an AC unit. 
The pool just needs a ‘dumb’ ASHP so I will choose accordingly based on service / reliability / longevity.

I chose ( will finalise my choice ) for the units based on merit / suitability and what will serve my clients the best. 

Make sense, I'm really on the fence on going two outdoor devices (A2W(monobloc) and A2A(split air con) or just stick with one big A2W, but the flexibility of having really separate systems that don't have to switch modes, the more agile control for calling heat/cold by the FCU feels like a bonus but the extra space and potentially cost might push me the other way since the pros and cons are complex and there's no obviously clear winner for me.. 

 

Stiebel seems like an interesting brand.. but at some point the benefits of a slightly better COP don't seem to make it into real world savings sufficient (over device lifetime) to make a huge difference..

[Nickfromwales]

Stiebel is expensive, but after being hands-on with the installation, commissioning and setting to work of it, I am very impressed.
The controls system(s) are VERY comprehensive, and it benefits from temperature blending ( mixing ) sets which allow pinpoint accuracy when delivering cooling. The AHU can get water as cold as 10°C whilst the UFH can get a steady 15-16°C, simultaneously.

I have designed this house with an ethos of “prevention not cure”, so the A/C unit will likely not get much use. If necessary to cool that one 2nd storey room, then it is there to perform a task that it is not sensible to ask the whole-of-house MVHR system to do. Nor would it be capable, ergo it was something I mandated in my turnkey M&E “solution”. 

[puntloos]

15 hours ago, Nickfromwales said:

Stiebel is expensive, but after being hands-on with the installation, commissioning and setting to work of it, I am very impressed.
The controls system(s) are VERY comprehensive, and it benefits from temperature blending ( mixing ) sets which allow pinpoint accuracy when delivering cooling.

 

Have you compared this to the usual suspects e.g. mitsubishi, daikin?

15 hours ago, Nickfromwales said:

The AHU can get water as cold as 10°C whilst the UFH can get a steady 15-16°C, simultaneously.

I suppose the main question I have is that part where you're already powering AHUs with your stiebel, not sure why you're creating a separate air conditioner incl outside unit for just one room? I can certainly see the point of having water AHU or coolant AHUs but not sure why you're doing both. 

15 hours ago, Nickfromwales said:

I have designed this house with an ethos of “prevention not cure”, so the A/C unit will likely not get much use. If necessary to cool that one 2nd storey room, then it is there to perform a task that it is not sensible to ask the whole-of-house MVHR system to do. Nor would it be capable, ergo it was something I mandated in my turnkey M&E “solution”. 

 

Good ethos, that's what I was/am aiming at too, but was indeed thinking of running all my AHUs off the split device.

 

Edited April 22, 2023 by puntloos

[Nickfromwales]

On 22/04/2023 at 23:07, puntloos said:

Have you compared this to the usual suspects e.g. mitsubishi, daikin?

Not directly, no. I've read a lot on here re "the competition", however it's a "yes" in the case of Panasonic Aquarea and I am VERY impressed with those for the price, very impressed indeed. Fitting another 4 of them shortly for current turnkey clients, all with cooling requirements which the Panasonic does out of the box.

The Stiebel unit has all of internal compressor side completely encapsulated in EPS, and all of the internal pipework etc is heavily insulated with neoprene, and the inside of the chassis etc is all sound-deadened with more neoprene panels / self adhesive sound-deadening, and Stiebel really seem to have really gone to town on this ( noise pollution / local audibility ) and this thing is literally 'whisper-quiet'. The Panasonic isn't far behind it, to be fair.

For clarity, I have designed everything holistically to allow this unit to have a flow temp of sub 24^oC flow temp into space heating and a room internal temp of 20.5^oC ( which seems to be comfortable whilst standing still / sitting, but a little warm when undertaking any activity. All of this would of course be unachievable without the airtightness having also been detailed to the nth degree.

I am still gobsmacked at how few of the "big hitters" fail to pay proper attention to this type of detailing... instead they just pay it some lip service and those who don't know, don't know. But when the AT test is done, "Oh!", do they know THEN!. Obvs too late to do much about it by then though   Stable door / horse / etc.

 

On 22/04/2023 at 23:07, puntloos said:

I suppose the main question I have is that part where you're already powering AHUs with your Stiebel, not sure why you're creating a separate air conditioner incl outside unit for just one room? I can certainly see the point of having water AHU or coolant AHUs but not sure why you're doing both. 

I design bespoke for each client, so never is there any element of 'copy / cut & paste' with my M&E proposals. I am also a 3rd party external contractor and liable for my actions / the end results. This particular house has 500mm ICF walls, AT score of 0.88 ( but I defo expect that to improve after some tweaks and hope to see sub 0.6 or better ), AND it's the 2nd storey where I've recommended that the A/C unit is installed. This is a studio / recreational room and on a super-sunny but windy day it may be impractical or a nuisance to have the wind blowing a hoolie through there when the occupants are trying to purge / cross-ventilate to have the room comfortable to use. This is NOT a bedroom, so the issue of 'summer overheating" shifts from a manageable purge / temp decrease before bedtime to a room requirement of "nice" all day / any day, on demand. With a PH there is no switch to flick to raise or lower the temp ergo I was firm on my specification here.

In honesty the unit may never get used, but anyone who has an A/C unit and uses it in the summer will tell you in an instant that it makes that room / space absolutely wonderful to be in, with an almost "fresh" feeling. When the windows can be opened the clients will absolutely do so, so would I, so would you, but if it's 24/25^oC or more outside then that's the temp that room will then instantly raise to. For sub £3k for a quality Mitsubishi unit, plus the benefit that this unit will offer heat also in the same price tag, then on a build which is the ouch side of 7 figures, £3k is a price that I thought worth purchasing some insurance with. If it was my house I would use it routinely, and my son is up in the attic of my leaky stone box in Wales and without his A/C the room would be unusable for at least 3 months of the year. As it stands he has many unwanted visitors in the summer, eg some of my other kids going up there to bunk for the night because his room is just so damn pleasant to be in. I'm downstairs sweating my arse off, with the house at 22^oC or more, and his room you could bloody well keep meat fresh in! 🥶

 

In the above clients home I also fine-tuned the design for the MVHR; so that it had a fresh inlet at one side of the room and an extract at the opposite side to absolutely maximise on the air quality up there.

Also remember that with cooling via MVHR, you need to use a lot of boost, so, the whole house would then have the elevated flow rates and possible audibility / compromise caused by it. I think it would be a shame ( aka a bad design ) to have to impact the entire household just because one room was problematic ( for the sake of £2-3k anyways ). If the clients come back to me in 3 years time and say it's never been used, I'll buy it back off them. That's how sure I am that it will get used. Folk who build to this standard PH / PH+ / NZEB etc become a little "bedazzled" with the nonsense that the sales-folk offer up, which is often just generic regurgitation of stuff they heard someone else say, and very rarely ( or more like almost never in my experiences over the last 8 years of 'PH' ) make their comments absolutely specific to the dwelling and the occupants, and life beyond moving in. I have to be held accountable for things to work, not just to fit, so I have a very different ethos to some others out there.

In a nutshell, that's why I specified this home this way  The next one may be different, as will the one after that!

 

On 22/04/2023 at 23:07, puntloos said:

Good ethos, that's what I was/am aiming at too, but was indeed thinking of running all my AHUs off the split device.

In your instance this would either need the AHU's 'blowing' directly into the spaces you wish to cool, or having a second fully insulated distribution duct network ( if you wanted to centralise for eg ). Is this as the primary heating, or is it a lamination over the UFH as an auxiliary system for targeted heat / cool? 

[puntloos]

14 hours ago, Nickfromwales said:

Not directly, no. I've read a lot on here re "the competition", however it's a "yes" in the case of Panasonic Aquarea and I am VERY impressed with those for the price, very impressed indeed. Fitting another 4 of them shortly for current turnkey clients, all with cooling requirements which the Panasonic does out of the box.

The Stiebel unit has all of internal compressor side completely encapsulated in EPS, and all of the internal pipework etc is heavily insulated with neoprene, and the inside of the chassis etc is all sound-deadened with more neoprene panels / self adhesive sound-deadening, and Stiebel really seem to have really gone to town on this ( noise pollution / local audibility ) and this thing is literally 'whisper-quiet'. The Panasonic isn't far behind it, to be fair.

For clarity, I have designed everything holistically to allow this unit to have a flow temp of sub 24^oC flow temp into space heating and a room internal temp of 20.5^oC ( which seems to be comfortable whilst standing still / sitting, but a little warm when undertaking any activity. All of this would of course be unachievable without the airtightness having also been detailed to the nth degree.

I am still gobsmacked at how few of the "big hitters" pay proper attention to this type of detailing... instead they just pay it some lip service and assume that those who don't know, don't know. But when the AT test is done, "Oh!", do they know THEN!. Obvs too late to do much about it by then though   Stable door / horse / etc.

 

Ha, so which of the big hitters to avoid?

My current shortlist is Mitsubishi (seems to have the lowest noise, highest cop of the 'common' brands) and Viessmann, somewhat the 'BMW' of the brands, that just upgraded their R32 line.

 

14 hours ago, Nickfromwales said:

 

I design bespoke for each client, so never is there any element of 'copy / cut & paste' with my M&E proposals. I am also a 3rd party external contractor and liable for my actions / the end results. This particular house has 500mm ICF walls, AT score of 0.88 ( but I defo expect that to improve after some tweaks and hope to see sub 0.6 or better ), AND it's the 2nd storey where I've recommended that the A/C unit is installed. This is a studio / recreational room and on a super-sunny but windy day it may be impractical or a nuisance to have the wind blowing a hoolie through there when the occupants are trying to purge / cross-ventilate to have the room comfortable to use. This is NOT a bedroom, so the issue of 'summer overheating" shifts from a manageable purge / temp decrease before bedtime to a room requirement of "nice" all day / any day, on demand. With a PH there is no switch to flick to raise or lower the temp ergo I was firm on my specification here.

In honesty the unit may never get used, but anyone who has an A/C unit and uses it in the summer will tell you in an instant that it makes that room / space absolutely wonderful to be in, with an almost "fresh" feeling. When the windows can be opened the clients will absolutely do so, so would I, so would you, but if it's 24/25^oC or more outside then that's the temp that room will then instantly raise to. For sub £3k for a quality Mitsubishi unit, plus the benefit that this unit will offer heat also in the same price tag, then on a build which is the ouch side of 7 figures, £3k is a price that I thought worth purchasing some insurance with. If it was my house I would use it routinely, and my son is up in the attic of my leaky stone box in Wales and without his A/C the room would be unusable for at least 3 months of the year. As it stands he has many unwanted visitors in the summer, eg some of my other kids going up there to bunk for the night because his room is just so damn pleasant to be in. I'm downstairs sweating my arse off, with the house at 22^oC or more, and his room you could bloody well keep meat fresh in! 🥶

 

In the above clients home I also fine-tuned the design for the MVHR; so that it had a fresh inlet at one side of the room and an extract at the opposite side to absolutely maximise on the air quality up there.

Also remember that with cooling via MVHR, you need to use a lot of boost, so, the whole house would then have the elevated flow rates and possible audibility / compromise caused by it. I think it would be a shame ( aka a bad design ) to have to impact the entire household just because one room was problematic ( for the sake of £2-3k anyways ). If the clients come back to me in 3 years time and say it's never been used, I'll buy it back off them. That's how sure I am that it will get used. Folk who build to this standard PH / PH+ / NZEB etc become a little "bedazzled" with the nonsense that the sales-folk offer up, which is often just generic regurgitation of stuff they heard someone else say, and very rarely ( or more like almost never in my experiences over the last 8 years of 'PH' ) make their comments absolutely specific to the dwelling and the occupants, and life beyond moving in. I have to be held accountable for things to work, not just to fit, so I have a very different ethos to some others out there.

In a nutshell, that's why I specified this home this way  The next one may be different, as will the one after that!

Ha, yes my reasoning is the same, prevent rather than regret.

14 hours ago, Nickfromwales said:

 

In your instance this would either need the AHU's 'blowing' directly into the spaces you wish to cool, or having a second fully insulated distribution duct network ( if you wanted to centralise for eg ).

I debated centralising but figured local cooling with a standard A2A would be more responsive, plus it would allow, theoretically, to get heat from one area and into another (or vice versa).

 

Either way, my current plan, like yours, is to have the A2W system do 'most of the work' in my passivhaus, potentially even a little cooling, but have 4 FCU (or AHUs? Is that the same thing?) to do localised temperature management. Most passivhauses work fine, but specific small rooms (in particular bedroom, in summer, with 2 humans in there..) need extra work.

 

Therefore my preferred option is one A2W (mitsu ecodan) and one A2A with 4 FCUs (mitsu split)

Option B might be a lot cheaper and is probably capable enough, which is a single A2W (mitsu, or perhaps viessmann) that does both UFH as well as DHW and cooling with FCU. I just don't quite understand the detail, but I think I know it will struggle heating and cooling at the same time and you have to do some clever switching of modes..

 

14 hours ago, Nickfromwales said:

Is this as the primary heating, or is it a lamination over the UFH as an auxiliary system for targeted heat / cool? 

 

[Nickfromwales]

11 minutes ago, puntloos said:

but have 4 FCU (or AHUs? Is that the same thing?

FCU's are dumb and AHUs are clever, in a nutshell.

[Nickfromwales]

6 hours ago, puntloos said:

Ha, so which of the big hitters to avoid?

My current shortlist is Mitsubishi (seems to have the lowest noise, highest cop of the 'common' brands) and Viessmann, somewhat the 'BMW' of the brands, that just upgraded their R32 line.

Any that don't employ / have an M&E consultant or provide a detailed breakdown with reasons / rationale etc. Also a lot of architects say they can sort this for you, but then palm it off and there's zero synergy / harmonisation of the installed equipment.

 

The Stiebel is German and I reckon it's the Mercedes to your BMW, but I'd really like to pull these apart to properly examine / compare them. I avoided both Samsung and Mitsubushi at the outset as none of their tech dept.'s wanted to speak to me to help design for such low-energy dwellings or discuss cooling. Samsung guy actually put the phone down on me when I said that cooling did work with their units and that I knew of folk who had got them to do so, ffs.

I rang Panasonic and the young, keen guys in tech-support were brilliant by comparison, immensely helpful. The product is robust, and I'm very happy with these units. They look a little utilitarian, that's all, but these aren't really on show as the pride and joy so I am struggling to see why anyone needs to pay more. Same warranty is offered by most ( 7 years iirc ) so they are what I'm fitting these days until someone demonstrates something much better to me, for not much more money.