passive house and ufh

[joth]

1 minute ago, Adrian Walker said:

 

 

The problem is educating people,  especially estate agents

Totally agree, this is why I almost fell down the stairs when the estate agent who visited us to make the valuation said he'd had punters walk in off the street asking if they had any more passivehauses for sale, like ours!

That was 2021. When we bought the house from that estate agent in 2018 (pre retrofit), I had only just heard of passivehaus myself, and they certainly hadn't!

So things are changing, and probably even more rapidly with events of the last 12 months 

[Dan F]

5 hours ago, Mr Blobby said:

 

Correct.  AFAICS there is no heating system specified in my PHPP spreadsheet, only heating demand.

 

Back to the OP's original question, UFH is a no brainer I think because of cooling potential and low temps for heating.

 

Also changing a window size should be no big deal.  My architect shares the PHPP sheet with me so the OP's architect shold be doing similar. 

 

 

PHPP Does include heating and cooling systems and calculates PER demand based on this.  That said, this isn't relevant for "PH Classic" using the standard criteria, and only becomes important for "PH Plus/Premium" where PER is important.

 

I've just been providing all the M&E information for our build, which includes ASHP efficiency, UFH flow temp, UVC specs, WWHRS specs etc.

 

[PeterW]

54 minutes ago, Adrian Walker said:

The problem is educating people,  especially estate agents

 Pretty sure someone on here (Jeremy possibly ..?) was told BH an agent his near passive place was worth 10% less or something due to it being “non standard”… 

[Russdl]

38 minutes ago, Dan F said:

PHPP Does include heating and cooling systems and calculates PER demand based on this.  That said, this isn't relevant for "PH Classic" using the standard criteria, and only becomes important for "PH Plus/Premium"

That will count for my lack of any recollection of entering a heating system in the PHPP - we just went for ‘Classic’ but I think we’re probably close to ticking the ‘Plus’ box as it happens. 

[Russdl]

3 minutes ago, PeterW said:

Pretty sure someone on here (Jeremy possibly ..?) was told BH an agent his near passive place was worth 10% less or something due to it being “non standard”… 

Yes, I think it was Jeremy. A relative tsunami of water has flowed under the bridge since that comment though.
 

We’re not going anywhere but I suspect if I were to show an Estate Agent/prospective purchaser my monthly utility bill it would generate a great deal of attention in the current climate. 

[Gone West]

7 hours ago, Russdl said:

Actually, thinking about it (it’s been a while since I did my PHPP) a heating system isn’t specified. The PHPP just tells you what the heat requirement will be - you choose what to do with that information. 
 

Any other PHPP users confirm my recollection??

IIRC when I did my PHPP runs in 2010 you could specify a compact heat pump unit supplying warm air through the MVHR which calculated the space heating load and whether that was sufficient on it's own to maintain the required internal temperature.

[Gone West]

1 minute ago, Russdl said:

Yes, I think it was Jeremy. A relative tsunami of water has flowed under the bridge since that comment though.
 

We’re not going anywhere but I suspect if I were to show an Estate Agent/prospective purchaser my monthly utility bill it would generate a great deal of attention in the current climate. 

When we sold our PH, not certified, in 2021 we had several buyers bidding against each other for the house, which sold for way above the asking price.

[ProDave]

I think if we decided to sell, I would not be trying to emphasise anything like "near passive house"  I would just be highlighting the EPC A.  Buyers are only just starting to take note of the EPC having been ignoring them for years, then wondering why their EPC F house costs a fortune to heat and suffers from damp and mould.

[Iceverge]

19 hours ago, Kelvin said:

What is the advantage of getting certified anyway? I assume it costs money to do so. I’d have though that near passiv gets you 99% of the benefit without the apparent hassle and complication. 

 

Passivhaus certification will come with a reem of documentation and photos as long as your arm. Importantly detailing the actual build, not the on paper design.

 

More than happy to live in our passivish/passive house as I could see it being built and was able to verify it myself.

 

 I wouldn't trust a non certified "passive" house as far as I could throw it. Most I've encountered have  double glazing, solar stapled to the roof, an "eco" stove, and airtightness levels so good that it didn't need to be tested. 

[jonM]

On 02/02/2023 at 20:15, JohnMo said:

With an ASHP to get best efficiency you need as low a flow temp as practical. UFH you can have flow temps in the 25 to low 30s depending on outside temperature. Radiators will always flow warmer than UFH, just because the surface area of the emitter is smaller.

 

A steady low temperature flow with UFH, very stable house temps.

 

PH don't need much heat, but still likely to need up to 10W/m2. So a 200m2 house is going to need 2kW at -3/4 degs. Or 48kWh per day.

All good advice but it is quite possible to use radiators as we do in our passive house. They work fine and are very controllable and easy to use. There are no cold spots, no draughts and even heat throughout the house so you can put the radiators any where in the room. The radiators should however be oversized so that flow temperatures are low to ensure efficient use of the ASHP. Flow temps wont be quite as low as UFH but not far off. 

[jack]

15 hours ago, PeterW said:

 Pretty sure someone on here (Jeremy possibly ..?) was told BH an agent his near passive place was worth 10% less or something due to it being “non standard”… 

 

I believe the term being discussed at the time was  "eco" house.

 

If I ever sell ours, my focus will be on getting our energy bills in front of potential buyers. Passivhaus doesn't mean as much to most as very low bills.

[Kelvin]

5 hours ago, ProDave said:

I think if we decided to sell, I would not be trying to emphasise anything like "near passive house"  I would just be highlighting the EPC A.  Buyers are only just starting to take note of the EPC having been ignoring them for years, then wondering why their EPC F house costs a fortune to heat and suffers from damp and mould.

Exactly. 99% of buyers will have no idea what a passive house is. Many will now care a bit more about how much it costs to run so sticking the utility bills under their nose will  be a good selling point. I can see old draughty expensive to run houses becoming harder to sell if energy costs and interest rates remain high. 

Edited February 8, 2023 by Kelvin

[Iceverge]

41 minutes ago, Kelvin said:

can see old draughty expensive to run houses becoming harder to sell if energy costs and interest rates remain high. 

 

I think they already are. And not before time. 

[SuperJohnG]

On 02/02/2023 at 20:15, JohnMo said:

PH don't need much heat, but still likely to need up to 10W/m2. So a 200m2 house is going to need 2kW at -3/4 degs. Or 48kWh per day.

 

That's 24 quid a day at the current rate of 50p / kWh. That's a lot of money..just in electricity. I hope the numbers are much less in mine when I finish. 

[Russdl]

@SuperJohnG If it’s -3/-4 then it’s almost certain to be a high pressure day with clear skies (perhaps a bit of mist/fog to start with) so the vast majority, and probably in excess of those required 48kWh will be provided by solar gain if you build to anything like passive standards. 
 

Our gaff fits roughly with those figures posted and for the last 3 nights it’s been -4 to -5 overnight with highs of +6 to +9 during the short sunny days. The heating hasn’t come on in the last 3 days and I don’t expect it will do today (currently -3 outside). 

[Nickfromwales]

15 hours ago, Adrian Walker said:

I totally agree, a PH will have lots of proof that it was built well and correctly.

A self-builder is more than capable ( most do anyways ) of documenting, with pictures, the methods of construction for the dwelling. Fabric standards etc become irrefutable then, plus the seller would then be able to show statistical data from the solar inverter / electric bills etc and effectively ( and factually ) demonstrate the very low running costs of the property as actual facts / figures. Selling with these credentials should sort the wheat from the chaff.

Soon there will be a better clientele, but better builders will need to come first.

[Nickfromwales]

7 hours ago, SuperJohnG said:

 

That's 24 quid a day at the current rate of 50p / kWh. That's a lot of money..just in electricity. I hope the numbers are much less in mine when I finish. 

If you only need a few days of heat a year it's free!! The revenue and mitigated costs over summer will have made you 'energy rich' and will provide for / contribute towards winter space heating ( if all designed correctly / thoughtfully ).

Best not to focus on the bits that cost you, think of what didn't cost you and do the maths properly  

[JohnMo]

8 hours ago, SuperJohnG said:

That's 24 quid a day at the current rate of 50p / kWh

Not sure where you are getting your electric or gas from, gas is 10p and electric 34p.  With a Heat pump and a CoP of 3, that's around £5 a day not £24.

[ProDave]

8 hours ago, SuperJohnG said:

 

That's 24 quid a day at the current rate of 50p / kWh. That's a lot of money..just in electricity. I hope the numbers are much less in mine when I finish. 

I don't know where you are but it's capped at 33p per kWh here.

 

If the required 48kWh was delivered with an ASHP at a COP of 3, that's 16kWh of electricity at a cost of £5.28  That is not so bad is it?77

 

EDIT: JohnMo beat me to it posting the same thing.

[Thorfun]

11 hours ago, jonM said:

All good advice but it is quite possible to use radiators as we do in our passive house. They work fine and are very controllable and easy to use. There are no cold spots, no draughts and even heat throughout the house so you can put the radiators any where in the room. The radiators should however be oversized so that flow temperatures are low to ensure efficient use of the ASHP. Flow temps wont be quite as low as UFH but not far off. 

Just because you can though, in my opinion, why would you go for radiators instead of ufh? Why take up valuable wall space with over sized radiators that won’t often be used when you can hide it all under the floor and keep it out of sight. Radiators just don’t make sense to me in a modern well built house. with the obvious luxury of a towel radiator in a bathroom to that warm fluffy towel to wrap yourself in post cleaning. 

[jack]

8 hours ago, SuperJohnG said:

That's 24 quid a day at the current rate of 50p / kWh. That's a lot of money..just in electricity. I hope the numbers are much less in mine when I finish. 

 

[Just noticed Johnmo and Prodave beat me to it on the price and ASHP COP]

 

Also, depending on where you live, it probably doesn't stay that cold for the whole 24 hours. Admittedly we're in the southeast, but even during a very cold period it would be unusual for the temperature not to get well into single positive figures during the day during winter. Different if you live in the Highlands I guess 

 

That very cold week we had in the south east recently was the first time in the 14 years we've lived in our current town that the average temperature was below zero for several days.

[ProDave]

The coldest week we had so far this winter with -10 at night and not above 0 in the day, my ASHP used 96kWh in that week heating the house or 13kWh per day.  That would have been a cost of £4.29 per day.  Yes it's colder in the Highlands, especially over on the east side.

 

That's a heat input of about 39kWh per day or 1.6kW continuous, which is lower than the calculated heat loss from Jeremy's spreadsheet, but incidental gains would account for the rest.

[Kelvin]

From memory you have a relatively small output ASHP?

[ADLIan]

2 hours ago, Nickfromwales said:

A self-builder is more than capable ( most do anyways ) of documenting, with pictures, the methods of construction for the dwelling. Fabric standards etc become irrefutable then, plus the seller would then be able to show statistical data from the solar inverter / electric bills etc and effectively ( and factually ) demonstrate the very low running costs of the property as actual facts / figures. Selling with these credentials should sort the wheat from the chaff.

Soon there will be a better clientele, but better builders will need to come first.

 

Photographic evidence of build quality (insulation levels, dealing at junctions, preventing thermal bridging etc) is now part of the Building Regs. Requirement of the 'new' 2021 Approved Doc L, effective mid 2022, for all new dwellings.

[jonM]

1 hour ago, Thorfun said:

Just because you can though, in my opinion, why would you go for radiators instead of ufh? Why take up valuable wall space with over sized radiators that won’t often be used when you can hide it all under the floor and keep it out of sight. Radiators just don’t make sense to me in a modern well built house. with the obvious luxury of a towel radiator in a bathroom to that warm fluffy towel to wrap yourself in post cleaning. 

Underfloor heating can be hidden, but therein lies the problem. If something does go wrong either with the installation or the operation, the pipework is under screed, difficult to track down and very intrusive fix. In a passive house, you can put the radiators out of the way, mine have rather a nice architectural quality to them, and my floors are not cold because they are well insulated. Controls are more complex on ufh and therefore there are more things to go wrong. As an example, different temperatures in bedrooms is easier to achieve with radiators. I know the overwhelming preference at the moment seems to be for ufh, but we have no regrets over choosing radiators.