Passive House verses A1 Rated House

runningman01

Hi,

I would love to build a bespoke passive house (~220m^2, medium spec, nothing fancy). From my research it seems this will add 30-50k to construction costs when using a contractor and 30-50k for having to use an architect (full service including passive design, on site support etc.) This would be a 60-100k premium for an estimated annual heating cost saving of <300 euro. These figures are very rough and I may be off but there is certainly a large premium involved with a bespoke passive house that is not economically justifiable in my opinion. Is this the general consensus or am I incorrect?

How good is a A1 rated house's thermal performance in reality as the thermal bridges would probably not be as well designed as a passive house's ones? I know of many A2 rated houses (~200-250m^2) that are assigned a 25-50 kWh/m^2/year heat demand but still rely on an 15kW heat pump. I know that heat pump will provide hot water and for peak load. I'm no expert but are these house not performing as designed or are their heating systems oversized? I imagine it is both or I would more heat demand driven.

dbas

https://www.boards.ie/discussion/2058286543/passive-house-verses-a1-rated-house

Any house can be an A1 if you put enough PV on it.

Passive houses are carefully designed and detailed to practically eliminate thermal Bridging and create an airtight fabric and reduce heat demand and minimise overheating in summer.

I'd question the 50k addition in cost. Savings could be made by simplifying the construction

sydthebeat

https://www.boards.ie/discussion/2058286543/passive-house-verses-a1-rated-house

most A2 rated houses of an average size of 200-250 sq m do not require 15KW heat pumps.

On average im seeing most heat pumps are in the range of 5 - 10 KW

I'm no expert but are these house not performing as designed or are their heating systems oversized?

The BER system is NOT a design tool, and not designed to be one either. Yes some heating designers will pull figure from it as part of their service, but it shouldn't be used as a comment on the specific energy demand of the dwelling.

whereas the passive design package is an EXACT calculation of the energy demand of a specific house. Thats why passive houses have such small capacity heating systems. The designers can calculate the demand to a very specific degree, and all assumptions are pushed to the worst case scenario, which results i teh heating systems being well able to meet the energy demand.

mike_2009

I'm building a Passive House this Summer. 102m2. I'd say it's about 10% more expensive but I was lucky I had the Architect do the PHPP and design from the outset a few years ago when their fees were cheaper. Just getting around to building now. The detailing is immense though and you need a good builder to pull this off. I'm going timber frame and doing the air tightness myself. You can do the PHPP design course yourself and do the calcs, it's the actual build details that need the attention to get the air tightness and avoid thermal bridging. Wish it was taught in school! There are air tightness courses you can do yourself too, not sure how much you want to take on though. So, yes you could spend 100K on this easily....

ColemanY2K

i too am building a passive house. 197m2 self build bungalow.

i spent two to three years studying passive house design at home before starting. i bought the passive house planning package and subsequently designed the house myself - it isn't rocket science. however i reckon i've spent thousands of hours mulling over the details and you do have to emphasise and re-emphasise to the trades how to do things and believe me many think i'm a bollocks or just eye rolling for telling them how to do things they think they've been doing right for years but when it comes to passive you've got to nail the detail. unfortunately the blocklayer didn't follow my detail and made an error at window cill level which would have meant unacceptable heat losses. luckily i will be able to remove the offending soap bars in the next fortnight or so and replace with pir to ensure the cold bridging issue is eliminated but its an example of where things can go wrong if attention to detail is not adhered to.

overall i reckon my house will cost an extra 8 to 10k to build over an A1 rated house. heating demand will be just 11kWh/m2/year according to phpp, significantly less than the max of 25kWh/m2/year required to achieve A1. however the extra building cost will be somewhat offset by savings made not just with energy bills but with a smaller heat pump, potentially knocking a couple of grand off the capital cost.

the estimated final cost is coming in at 205k at the moment.

imo passive house is the holy grail and the buildings regs should reflect it.

dbas

https://www.boards.ie/discussion/comment/120343462#Comment_120343462

Well done. It is the holy grail for house building. A no brainer you consider the heating bills over the next 20 years, and the savings therein.

Great point about the smaller heat pump. Get one with a lower gwp refrigerant too if possible.

I've one question for you. You've compared costs against an A1 house. In my experience A1 is not achievable without PV. Do you have pv planned for your house. (I'm wondering does the 8-10k PH cost uplift include PV or did PH build allow you to remove PV from the costs?

ColemanY2K

https://www.boards.ie/discussion/comment/120344384#Comment_120344384

PV is included in the costs. I am planning to install a 7kwp system. Sourcing the components like inverters and panels in Ireland is difficult as wholesalers have reportedly recently decided to sell solely to installers. I have a way around that by purchasing panels from a solar retailer ( https://shop.gwl.eu/ ) in the Czech Republic and rest of the kit elsewhere. We'll erect the hardware (ground mounted panels in the garden feeding the inverter in the shed) and the electrician wiring the house has allowed for commissioning the system.

The kit and installation will cost 5k versus circa 10 to 15k if I was to go with a specialist to supply and install the kit. The sparky will wire it in less than a day - coincidentally he is installing his own system at the moment.

Cheers for the tip on the heat pump.

Let me know if you need any more info. Happy to advise.

dbas

https://www.boards.ie/discussion/comment/120348063#Comment_120348063

You've done really well limiting the cost uplift with your passive House.

Well done. It's well worth doing! I bought an A2 house off plans and it's performance is pretty poor really.

What heat pump were you thinking of installing.

ColemanY2K

https://www.boards.ie/discussion/comment/120348223#Comment_120348223

A local distributor has quoted 10k plus vat (supply only) for a 8kW Samsung air source heat pump, 200/60 litre wellmaster cylinder, underfloor heating and all the bits and bobs to go with it.

I noted they are saying the heat pump has a low GWP refrigerant as mentioned as something to look out for by you in an earlier post. It seems most contain R32 these days

It's a 4 bed house so thinking of upping the size of the cylinder.

dbas

https://www.boards.ie/discussion/comment/120348578#Comment_120348578

Who's sizing your underfloor system?

I've an SR 50 sheet somewhere.

I've a 4 bed house too with a 200l tank.

Works OK. One thing I hate about heat pumps is hot water priority. If tank is cold and house is cold, the tank gets priority.

Your house won't get cold, but I've heard of people getting separate systems for water and heating.

Some heat pumps are still using r134a.

Bigger tank would be handy. In a normal house you'd get additional tank losses, but in yours, it'll be more free heat for your mvhr