why passive house?

[mjc55]

I have seen it said a few times on the forum about wanting to build to passive house standard (or as near as) but not being bothered about it being certified passive.

 

In fact I have said the same myself!

 

I am now asking myself why?

 

Is it because the idea of passive is great but the thought of building to a standard but not actually reaching it is scary!

 

Thoughts?

[joe90]

I built to passive principles, probably not actually achieving a “pass” and had no intention of getting certification. The driving principle for me was a comfortable house that was affordable. My thought was if I ever sold the house showing how cheap it was to run would have more clout than a certificate that most buyers would not even understand. Even now i believe a lot of buyers take very little notice of the EPC rating (presuming it’s accurate which I believe a lot are not!!!!).

Edited July 24 by joe90

[garrymartin]

Our brief to our architects says we want a Passivhaus building but not to the extent that it constrains the way we want to live in any way. If we can achieve both, bargain! But if not, the ability to certify to Passivhaus criteria will be the element that we flex, not how we want to live.

 

I'm in two minds about whether to certify it if we do meet all requirements. I like the idea of being able to say it is certified, but I'm not sure the expense is really worth it. As @joe90 mentions, I think any future occupants will be more interested in how little it costs to run and how much energy it produces rather than a certificate. I think this will be particularly interesting when (if) the Future Homes Standard and any requirement like that in Scotland ever makes its way to England regarding "Passivhaus-like" requirements...

Edited July 24 by garrymartin

[G and J]

52 minutes ago, garrymartin said:

Future Homes Standard

So is this Passivehaus Lite?

[IanR]

49 minutes ago, mjc55 said:

Is it because the idea of passive is great but the thought of building to a standard but not actually reaching it is scary!

 

Not at all, achieving the standard is not particularly difficult for the self-builder. Probably because the standard is very well considered, setting achievable targets for justified reasons that deliver a return. 

 

Certification is a personal choice. It does cost extra, but doesn't tell you anything about your home that you don't already know.

 

1 hour ago, mjc55 said:

why?

 

Living in a PH house has given me more significant reasons as to "why", than I had when I chose to build one.

 

I initially wanted reduced bills, I was building a long-term family home. Since the targets are significantly higher than Building Regs at the time, especially for a conversion, I did wonder if they'd be achievable and wasn't too concerned if I didn't quite get there. I also knew that I wanted more glazing than a PH house should really have.

Through the Design phase the PHPP software really informed my decisions, and demonstrated where budget was best spent to achieve the overall building performance. The PH targets became my targets, as the PHPP software showed what changes were needed and didn't leave me guessing whether or not I had too much roof light area or not enough insulation. Had I just been building "better than regs", there are loads of minor changes I wouldn't have made, because I wouldn't have been using the tools that showed me exactly how the building would perform without those changes.

 

While PH does deliver the low bills that I was after, the greater impact is comfort. I believe it's the lack of temperature gradients across rooms, with no perceivable convection currents, stable internal temps across the day, no perceivable air infiltration, the quietness of 3G glazing and while not specifically PH, the solidity of blown cellulose insulation gives rise to a comfort level I've not felt in any other building.

[IanR]

24 minutes ago, G and J said:

So is this Passivehaus Lite?

 

Announced in 2019 it's due to come in force in England in 2025 via a significant Building Regs update and is claimed to deliver a 75-80% reduction in day-to-day CO2 from residential homes.

 

The consultation closed in March this Year and we'll hopefully hear soon how they expect to achieve the reduction, assuming Labour stick to the published timing.

 

Not much detail is yet known, although the previous government had announced the banning of fossil fuel boilers for new homes would be part of it.

 

The PassivHaus Institute are not involved with the FHS.

Edited July 24 by IanR

[SteamyTea]

The Laws of Thermodynamics makes it is technically easy to build a low energy usage house, they will just not look very nice i.e. square floor plan, small windows, thick walls, and loads of MVHR pipework in the loft.

The CO_2e part is really out of peoples control, that is down to the nation's generation mix, which makes the statement about designing a house that used x amount less a bit of a nonsense.  OK you can stick as fair amount of PV on a roof, and you should, but that only lowers the local CO_2e volumes produced, does not make much difference to the globe.

 

Edited July 25 by SteamyTea

[MikeSharp01]

7 hours ago, mjc55 said:

Is it because the idea of passive is great but the thought of building to a standard but not actually reaching it is scary!

 

Thoughts?

We did set out to build a certified Passive House (PH) and we are very close now to doing it although we may not certify as we now have other priorities. For us the lower impact on the planet, in the long term, was/is the key driver. I do tend to agree with:

 

9 minutes ago, SteamyTea said:

The CO_2e part is really out of peoples control, that is down to the nation's generation mix, which makes the statement about designing a house that used x amount less a bit of a nonsense.

 

while I think any impact is worth while and we will use a lot less of the local generation than many in our all electric house.

 

6 hours ago, IanR said:

Through the Design phase the PHPP software really informed my decisions, and demonstrated where budget was best spent to achieve the overall building performance. The PH targets became my targets, as the PHPP software showed what changes were needed and didn't leave me guessing whether or not I had too much roof light area or not enough insulation. Had I just been building "better than regs", there are loads of minor changes I wouldn't have made, because I wouldn't have been using the tools that showed me exactly how the building would perform without those changes.

Can't see how it could be done any other way really.

 

The costs are higher and the challenge more technical, my life partner - wife says she might have thought twice had she known just how technical is has become, because you are working with a bigger number of constraints which often result in difficult compromises. For instance - we, our situation, cannot now get PH certification without an ASHP in the mix - so we will fit one. As a self builder, who did not employ a PH professional at the design stage or an experienced PH Architect there were additional challenges. Instead I did a course on PH and the PH Planning Package (PHPP), read loads, worked with our architect and structural engineer to take their outline designs through the PHPP and make sure it would pass and once the design was finalised we have stuck to keeping the PHPP model up to date and building as close to as designed as we could. I feel that the Cold bridging element is the toughest aspect because the PH certified standard needs evidence of any cold bridges being worked through which we did twice because we changed the windows system during the build. (Went from Rationel to Norrsken) So things have changed a little. We also dropped the gas boiler idea early and changed the insulation from frametherm to blown cellulose which made the overall balance go a little awry, the insulation's U value goes from .35 - .38, but we brought it back by adjustments elsewhere. This, incremental change approach, is quite hard once the house is under way hence the ASHP became a requirement to get us down into the energy demand zone. 

[nod]

We are moving into our second build today Both well insulated Like forever home It’s just a label and will mean more to you than any future buyer 

I would make sure that you are happy with the rest of the build your main priority We fought planners on both occasions over trying to make us have  PV ruining  the look of our slate roof 

If I was to go down the route of Passive I definitely wouldn’t pay for someone to give a certificate telling me what I already know 

[MikeSharp01]

21 minutes ago, nod said:

If I was to go down the route of Passive I definitely wouldn’t pay for someone to give a certificate telling me what I already know 

Tend to agree, although, it rings a bit hollow having spent yesterday at a graduation ceremony for 600 Engineering and Science students all of whom got a certificate telling other people what the students and the staff already know so sometimes it is for other peoples consumption and holding it has a personal value. I also happen to think that the Passive House standard is now getting better understood and much more widely talked about so we may well be heading the way of more acceptability of the certificates value among buyers. 

[Dave Jones]

passive should really be the default for what is built. The market though wont pay the extra cost  to build them though. This is where the banks could incentivise by reducing rates for well built EPCA builds.

 

Octopus are starting by giving 5 years of no bills for houses built to their spec.

[G and J]

14 minutes ago, Dave Jones said:

Octopus are starting by giving 5 years of no bills for houses built to their spec.

I tried to engage with Octopus re the zero bills thing and they informed me they aren’t doing zero bills for self builders.

[Sparrowhawk]

1 hour ago, nod said:

If I was to go down the route of Passive I definitely wouldn’t pay for someone to give a certificate telling me what I already know 

 

It tells you what you already know, but when you come to sell it tells your buyer something they otherwise have to take on trust.

 

"Well insulated" and "airtight" and "not prone to overheating" - heard all those before from sellers and none were accurate.

 

1 hour ago, MikeSharp01 said:

For instance - we, our situation, cannot now get PH certification without an ASHP in the mix - so we will fit one.

 

This is where I dislike certification, and particularly the ideologically-motivated AECB retrofit certifications. I'd rather that certifications for building (or retrofitting) well-performing houses were adjacent to certifying low-carbon houses. Reward people for making low-energy houses without mandating (as AECB do) that they install a heat pump. Many will as time goes on but you can save a lot of energy even with a gas boiler in place.

[G and J]

I’ve approached this from the other direction.   When we started planning our build, (informed by TV programmes like Grand Designs) PH seemed like a daft idea, requiring houses with two foot thick walls, two acres of meadow for the GSHP, and 18’ deep concrete slabs and acres of glass so they looked like an Asda.  I suspect that’s still the image a high percentage of the population who have heard of PH have.

 

But I figured there would be elements that would be worth using on our modest home.  We were committed to disconnecting gas from the word go, and that meant an ASHP as I’d already learnt that GSHP wouldn’t work for us.   Airtightness and MVHR was clearly the way to go, so they were the first elements adopted.  I was very keen on a long underground pipe to feed the MVHR but concluded that that wasn’t yet proven technology and wasn’t one that the MVHR suppliers were happy with so ditched that, sadly.   Turns out our design had a sensible form factor anyway (2.75 if I’ve calculated it correctly), so that made me smile and feel we weren’t so bad.  We’ve not that much glazing and can’t take advantage of solar gain because of the restrictions of the site, but we do have an east/west ridge on our bog standard 40degree pitched roof so south facing solar PV should be productive and offer a quick payback especially with the slate saving.  Cold bridging is boiling my brain right now, and I think that’s the area I would fail most on as we will have to have a cheap strip foundation b&b construction and I’ll do my best but it won’t be the same as a polystyrene raft based build.  

 

What I’m ending up with is, I think, sort of a PH Lite, on a sensible budget, and where it won’t translate into volume house building is the extra time I’ll put in to airtightness.  But as the practices become more widespread and the kit makes it easier and MVHR becomes a basic then I’m sure airtightness will steadily improve.  So I’m starting to think that our house will be not an inspirational green build icon, but simply one of the earlier examples of the new basic houses of next decades volume builders.  

[Simon R]

10 hours ago, mjc55 said:

I have seen it said a few times on the forum about wanting to build to passive house standard (or as near as) but not being bothered about it being certified passive.

 

In fact I have said the same myself!

 

I am now asking myself why?

Like Joe90 we built to passive ideals but did not agree with certain aspects of the standard. In particular the need for and ASHP. The whole point of passive is a focus on energy reduction. A house built to them frequently doesn't consume enough energy to make and ASHP install sensible, the alternative of a low cost A2A makes more sense. Understanding the basics of passive build is fundamental to reducing inputs, certification isn't.

I can't overstate the benefits of living in a house built on the passive principles, it's an incredibly comfortable living environment.

[Andehh]

We built the most inefficient home possible, by the nature of a large bungalow in the shape of an 'H' effectively, with a lot of glazing, very high ceilings everywhere and simply put an extra £6500 ish into upgrading insulation everywhere we could and 'try for good airtightness (2.7)..... Then hoped for the best!

 

 (incl MVHR, ASHP, UFH, PV)

 

End result is bills of somewhere between £150 and £175 for our electricity for a warm house.

 

There is a pragmatic middle ground in everything, but don't compromise on a home design for the sack of savings £50 a month on bills....

 

 

[MikeSharp01]

9 minutes ago, Sparrowhawk said:

This is where I dislike certification, and particularly the ideologically-motivated AECB retrofit certifications. I'd rather that certifications for building (or retrofitting) well-performing houses were adjacent to certifying low-carbon houses. Reward people for making low-energy houses without mandating (as AECB do) that they install a heat pump. Many will as time goes on but you can save a lot of energy even with a gas boiler in place.

Sorry I perhaps was not clear. The reason we will have an ASHP is more nuanced than the AECB approach (was a member for about 5 years but have let that lapse.) On our original plan, 2018, we had a gas boiler - no problem getting PH requirements. We decided we didn't want gas for all the reasons we now understand so well. As I was quite taken with the work @TerryE had done with the Willis heaters that was, until late last year, our plan. However, when you go direct electric heating everything else needs tightening up to meet the energy limitations for the house which we did but now as we are further into the build the room for maneuver is limited. Then we noticed that the EPC system trips in and you cannot get a good EPC, see discussion elsewhere on this forum, with direct electric heating! So although we could get PH certification, just, the EPC would have been rubbish and as we feel the need for both we will adopt an ASHP to make it all hang together again - PH certification possible and a, hopefully, better that 100 EPC. For us the spin off will be very low heating bills and a warm airtight home that matches our personal 'machine for living in' requirments - certificate or no certificate. So no different to anybody else really. SO I will now jump down from the head of this pin.

 

3 minutes ago, Andehh said:

End result is bills of somewhere between £150 and £175 for our electricity for a warm house.

Is that the annual cost?

[ProDave]

We built our first self build just over 20 years ago.  I knew nothing then of passive houses.  But coming from a 1930's semi with solid walls and high heating bills, the "standard" timber frame build of the time was very warm, comfortable and not outrageously expensive to heat.  but it had many shortfalls, mainly as I have discussed before, the huge amount of holes in the structure forced by building regs to have extract fans in so many rooms, and other "standard" things like a cat flap, a letter box and a non room sealed WBS.

 

In the time between that and starting our second build I did a spell of work for a local company building "low energy" modular homes.  I learned a lot about insulation, air tightness and MVHR from that.  So that is the principles we applied to out second self build.

 

My 2 main things, I wanted a heating load low enough to be satisfied by a small ASHP.  We have no mains gas, and I did not want an oil tank or bulk gas tank in the garden.  And I wanted air tight and mvhr with no unnecessary openings in the building structure.  So no cat flap or letterbox, no individual extract fans (that most of the time are just a hole to let heat out and draughts in) and an air tight structure.

 

We achieved that and are pleased with the result.

 

I think the term "Passive House" is confusing to the layman, they expect a house that needs no heating.  I don't think that is possible in most of the UK. 

[G and J]

14 minutes ago, ProDave said:

the term "Passive House"

Would be a good name for a care home.  

[Iceverge]

I remember a discovery documentary about rifle barrell design has remained static with 100 years after centuries of constant change. It basically reached an end point. 

 

Similarly, now nearly all cars have 4 wheels, wind turbines have 3 blades, every phone is a landscape shaped touchscreen. Unicycles and blackberrys are rare. There is a practical finishing line. 

 

Building regulations are a study in slow slow creeping incrementalism. They're heading towards PH and will get there evetually despite the standard being already 3 decades old. 

 

Why not skip to the end?

 

Everyone else is trying to sell you one of these. 

 

[G and J]

So, imagine in parallel universes that two almost identical builds were happening.  The only difference is that one is going for PH certification and the other isn’t. 
 

All build costs are the same apart from PH consultation stuff and PH certification and whatever else is needed to get a ticket.

 

How much extra do the PH certified project cost?

[JohnMo]

7 hours ago, Andehh said:

End result is bills of somewhere between £150 and £175 for our electricity for a warm house.

What for a year or month?

[nod]

10 hours ago, Sparrowhawk said:

 

It tells you what you already know, but when you come to sell it tells your buyer something they otherwise have to take on trust.

 

"Well insulated" and "airtight" and "not prone to overheating" - heard all those before from sellers and none were accurate.

 

 

This is where I dislike certification, and particularly the ideologically-motivated AECB retrofit certifications. I'd rather that certifications for building (or retrofitting) well-performing houses were adjacent to certifying low-carbon houses. Reward people for making low-energy houses without mandating (as AECB do) that they install a heat pump. Many will as time goes on but you can save a lot of energy even with a gas boiler in place.

At the end of the day It’s just a piece of paper As useful as a ten year warranty certificate 

In fact they could go in the same frame Hung in the loo 

[nod]

I am just listening to Andrew Marr on LBC Proposals for PV on all public buildings He said surely not on our beautiful council buildings There’s loads of ugly car parks that we could put them on He has a point 

[G and J]

2 minutes ago, nod said:

At the end of the day It’s just a piece of paper As useful as a ten year warranty certificate 

In fact they could go in the same frame Hung in the loo 

17 years after we finish our build our warranty paperwork will have long since been firelighters, the faded PassiveHaus Certificate will still be proudly displayed in the hall in the vain hope that it’ll help the valuation for the lifetime mortgage which we will need to replace the old wheeled campervan with a new thermonuclear (food waste based) powered hover van with integral health suite and coffee maker.   You never know, PH might become trendy and help sell in the future…