Passive Haus on a budget?

[bobberjob]

Hello all

 

We are converting a small agricultural steel frame barn to a house. The idea always was to use modern methods of construction to build a Passiv Haus.

 

As the budget will not stretch to everything at once which elements could be removed from the build and perhaps added later? Is there a pecking order of must haves?

 

Is living in a house built to current building regs such a bad thing anyway?

 

[Ferdinand]

Welcome to the forum.

[Gone West]

10 minutes ago, bobberjob said:

Is living in a house built to current building regs such a bad thing anyway?

 

The worst thing about current building regs. is the airtightness requirement. If you aim for a maximum of 1 ACH the rest of the regs. aren't too bad. If you can improve on the insulation levels so much the better.

[AliMcLeod]

Welcome to the forum. The first thing you need to decide is wherther you mean the officially accredited Passivhaus (which you pay for) or the lower-case passive house, which is not an official stamp, but where what you build has has much lower energy needs than building regulations require. In the latter case, the answer really does depend on where along the piece of string you want to stop. There are some quick wins (such as air tightness) that you should just do anyway, but other things will undoubtedly add cost if you choose to do them.

Edited March 27, 2019 by AliMcLeod

[PeterW]

Probably worth clarifying a couple of things first. 

 

PassivHaus is a standard that’s regulated and requires the property to meet a set criteria that is inspected  

 

Passive House principles are those that take those elements but don’t go after the standard and certification. 

 

In terms of getting to the standard then you will probably be limited by the fabric elements to start with, and then look to add the value add stuff such as solar etc later. Make sure the infrastructure and connections are in etc and work from there. 

[Big Jimbo]

My personal thoughts are that you should adopt a fabric first approach. That is make the actual building structure as good as you can. Design out as much of the Thermal Bridging that you can. Try and achieve very high levels of insulation in the floor, walls, and roof. Try and make the building as airtight as you can, and fit some decent windows and doors. If you do this you won't go far wrong.

[jack]

28 minutes ago, Big Jimbo said:

My personal thoughts are that you should adopt a fabric first approach. That is make the actual building structure as good as you can. Design out as much of the Thermal Bridging that you can. Try and achieve very high levels of insulation in the floor, walls, and roof. Try and make the building as airtight as you can, and fit some decent windows and doors. If you do this you won't go far wrong.

 

Yep, that's pretty much it.

 

As said above, airtightness is important, and becomes increasingly so as the volume of the building increases. Using standard building regs insulation but working towards, say, 1 ACH will make a noticeable difference. If you can afford more insulation, do that too.

 

Unlike insulation, which can only be improved by spending more money (twice the insulation is twice the cost), airtightness can be improved by careful planning and detailing. This needn't be expensive. I'm sure you could improve on building regs airtightness by a factor of 5 with relatively little extra cost.

 

It might also be worth searching "decrement delay" on the forum. Choosing an insulation material with relatively high decrement delay, such as cellulose or wood fibre, may improve the perceived thermal performance of the building for a given U-value. The main improvement is reduced peaks and troughs of temperature.

[Dreadnaught]

For information, my quote for Passive House certification was £2,129 + VAT. It seems to depend on the architect: I was told my quote was a bit lower because the architect was both a certified PH-designer and known to the certifier.

[bobberjob]

Blimey I only went for a cuppa and all this info - thanks everyone you are very welcoming.

 

It is the principle we are interested in not the certification. I have read as much of the forum as I can and absorbed much less but it is a fantastic source.

 

I am already leaning towards Warmcel as Mr Harris' piece on decrement delay.

 

thanks again

[jack]

Just now, Dreadnaught said:

For information, my quote for Passive House certification was £2,129 + VAT. It seems to depend on the architect: I was told my quote was a bit lower because the architect was both a certified PH-designer and known to the certifier.

 

All up? That really surprises me. As you say, the architect's particular situation is probably contributing to the cost being lower, but that seems to be a fraction of the cost I'd expect for full certification. It's been a long time but I'm sure we were expecting to pay three or four times that amount (including all modelling and inspections, etc), not taking into account the cost of more expensive hardware such as a PH-certified MVHR unit.

[Dreadnaught]

1 minute ago, jack said:

All up? That really surprises me. As you say, the architect's particular situation is probably contributing to the cost being lower, but that seems to be a fraction of the cost I'd expect for full certification. It's been a long time but I'm sure we were expecting to pay three or four times that amount (including all modelling and inspections, etc), not taking into account the cost of more expensive hardware such as a PH-certified MVHR unit.

 

Yes, all up. It included: "Initial Check", "Design Assessment" (the biggest part at £1064 + VAT), "Completion & Certification Processing" and "Passivhaus institute fee for certification". The only thing it excluded was the house plaque at £75 + VAT!

 

The PHPP modelling, etc., would be all be done by my PHPP consultant. I would estimate about £1,500 to £3000 + VAT for that.

 

In the end I chose not to go for certification for my build.

 

[kxi]

Hello, could you provide more details about your existing barn and the nature of the conversion? Esp. are you allowed to extend the envelope or not. This will help with more specific advice. The main reason for asking is steel frame may require a slightly different solution to most of those discussed on the forum.

Edited March 27, 2019 by kxi
for clarity

[jack]

40 minutes ago, Dreadnaught said:

The only thing it excluded was the house plaque at £75 + VAT!

 

You couldn't pay me enough to have that plaque on view anywhere in my house. From logo to colours to font selection to layout, I can't imagine how it could be made any uglier.

Edited to add:

 

[epsilonGreedy]

3 hours ago, bobberjob said:

Is living in a house built to current building regs such a bad thing anyway?

 

 

An overlooked point on this forum because leading contributors have pursued passive house performance with much enthusiasm.

 

The House Builder's Bible has a useful table showing the energy costs for the book's model house if built to past, current and passive house standards. The model house is 1722 sq ft.

 

Space and water heating annual costs using mains gas are:

 

£3,680 1975

£800    2013 standard

£224    Passiv House

 

These costs exclude standing charges. The passiv house is assumed to have PV and if the 2013 house had the same the water heating bill would be halved which would reduce the annual bill by 1/6th.

 

The same chapter then discusses other annual running costs, for example mains water and sewage for 3 people is about 2.5x more than the passive house heating costs. Then consider some domestic appliances: washing machine, tumble drier, kettle, dishwasher, fridge freezer and TV, the annual electric bill for these is 50% more than the passive house heating bill according to the book.

 

The numbers demonstrate there is no passive house magic point where holistic household annual running costs plummet. There are however some unhappy regions on the passive house pursuit curve to be avoided. Somewhere between a tested air change rate of 1 and 5 there is a zone where MVHR is not a happy buddy with a fairly air leaky house. Then there is the subtlety of decrement delay, getting this right means you can choose when in a 24 hour period to top up your heat reserves depending on the availability of free or cheap energy. If however all this new passive house thinking is configured poorly due to bad design or ignorant trades onsite then you can end up in the passiv house pit of despair that requires keeping the house warm with electric radiators consuming evening rate KwH or sweating in bed at night due to runaway solar gain.

Edited March 27, 2019 by epsilonGreedy

[lizzie]

Hello @bobberjob and welcome.  I’m a new build MBC timber frame built with passive standards of insulation, airtighness etc.  I’m in Worcestershire too.

[Bitpipe]

1 hour ago, jack said:

 

Yep, that's pretty much it.

 

As said above, airtightness is important, and becomes increasingly so as the volume of the building increases. Using standard building regs insulation but working towards, say, 1 ACH will make a noticeable difference. If you can afford more insulation, do that too.

 

Unlike insulation, which can only be improved by spending more money (twice the insulation is twice the cost), airtightness can be improved by careful planning and detailing. This needn't be expensive. I'm sure you could improve on building regs airtightness by a factor of 5 with relatively little extra cost.

 

It might also be worth searching "decrement delay" on the forum. Choosing an insulation material with relatively high decrement delay, such as cellulose or wood fibre, may improve the perceived thermal performance of the building for a given U-value. The main improvement is reduced peaks and troughs of temperature.

 

Passive or not, also think carefully about excessive solar gain and how to minimise it at the design stage.

 

Even a house built to the regs will suffer overheating.

 

[scottishjohn]

24 minutes ago, Bitpipe said:

Passive or not, also think carefully about excessive solar gain and how to minimise it at the design stage.

 

Even a house built to the regs will suffer overheating.

as its a conversion of  a building maybe you could do something very novel for over heating 

 like open a window !!.

you say its on a budget so maybe you not going with mega floor to ceiling windows  anyway --they are expensive  and thats where you mega solar gain will come from 

getting house insulated and air tight  should be primary concern i think 

concern on over heating would not be high on my list on a budget build

fabric first--

It would help if you stated a rough budget  + floor area of building --then people may direct you on best way to spend it

 

Edited March 27, 2019 by scottishjohn

[Bitpipe]

14 minutes ago, scottishjohn said:

as its a conversion of  a building maybe you could do something very novel for over heating 

 like open a window !!.

 

On a warm day, where the air outside is warm, opening a window makes no difference and may make things worse. Also, in an airtight house, you need to open two windows to create a through draft.

 

You also don't need a mega window to cause a problem - our kitchen window is 1600mm x 1200mm and is south facing. We didn't fit it with an external blind as it faces the neighbours gable but it does let in a lot of sun when it's lower in the sky (spring & autumn) and can quite quickly warm up that room.

 

We do use roof windows to purge the house in summer if the air temp is lower outside (i.e. in evening).

[scottishjohn]

so what would you say your average air temp is form april   to oct 

certainly up here there are not that many days in normal year where the air is 23-24c  or more for that period 

kitchen is not a good example as you make heat in there  when cooking .

Is this a thing that is prevalent in open plan houses  ?

 

[Bitpipe]

3 minutes ago, scottishjohn said:

so what would you say your average air temp is form april   to oct 

certainly up here there are not that many days in normal year where the air is 23-24c  or more for that period 

kitchen is not a good example as you make heat in there  when cooking .

Is this a thing that is prevalent in open plan houses  ?

 

 

I live in SE England  - inside the house is usually 22^oc all year round. Exterior was in the 30s for quite a chunk of the summer last year - 20s and high teens in the shoulder months.

 

We only use an oven in the evening to cook, the overheating we experience from that window can start from 10am unless we shade it internally.

[jack]

1 hour ago, scottishjohn said:

concern on over heating would not be high on my list on a budget build

 

It still needs to be on the list.

 

Our house would have been intolerable last year if we hadn't been able to cool the ground floor slab. We have external blinds on a lot of windows, but with a bit more foresight, external shading on a few more key windows would have reduced a lot of the overheating issues we face.

[lizzie]

Don't ignore overheating.  I had a real problem last summer.   I'm hoping measures taken over the winter will prevent it happening again to the same degree.

[ProDave]

2 hours ago, scottishjohn said:

so what would you say your average air temp is form april   to oct 

certainly up here there are not that many days in normal year where the air is 23-24c  or more for that period 

kitchen is not a good example as you make heat in there  when cooking .

Is this a thing that is prevalent in open plan houses  ?

 

When I lived down south in Oxfordshire, in a poorly insulated 1930's house, summer overheating was a problem, and very often the outside temperature was too high to cool the house, opening the windows would just let the hot air in quicker.  The only solution was a night purge, all windows wide open after dark and shut at sunrise.

 

Up here in the Highlands, the air is rarely warm enough to cause that issue and with decent insulation, overheating is not a problem we suffer.

[scottishjohn]

41 minutes ago, lizzie said:

Don't ignore overheating.  I had a real problem last summer.   I'm hoping measures taken over the winter will prevent it happening again to the same degree.

was hardly a normal summer  last year 

[lizzie]

@scottishjohn would still have been a problem.  Lack of shading on West and South and a lot of glass.  Hoping for a lovely but slightly cooler summer this year!