Passive house, early design stage - advice please.

CiaraG75

Hi everybody,

We are currently at the very early stages of design & are very interested in the possibility of building a passive house. We have done a lot of internet research but haven’t really spoken to any experts yet. We have loosely designed a plan that will hopefully work on our site, and would very much appreciate any advice on the following points…

Builders - what would be your advice on using “ordinary” builders vs experienced passive house builders? Is it better to have a kit house (timber frame or other) than a block-built house? And is either one more cost-effective?

HRV systems – on these boards / forums there has been a lot of discussion on these. We have again done a fair bit of research on ducting, positioning of the ducts, vents etc…. what we are really after is people’s experiences of how it has worked in reality. Can anyone give us any advice as to how their HRV system has worked for them? Pros & cons? Good installers / suppliers?

Heating: We are considering photovoltaic panels for hot water & a wood pellet burner to heat the house, with underfloor heating downstairs & radiators upstairs. We would prefer to have concrete floors upstairs with underfloor heating but what we have read so far seems to suggest that this can’t be done because of the HRV ducts. Can anyone refute this? Does anyone have experience of other heating systems that would work well other than wood pellet burners? We are open to suggestions.

Also on heating, does anyone have opinions / experience on using underfloor heating with hardwood flooring? We have read that it can cause warping – how much of a problem is this in reality? Would laminated / semi-hardwood floors work better?

Glazing: again, we have read loads on this, and it does seem to be a “how long is a piece of string” type of question! But what are your opinions? Is triple glazing worth the extra money? Is it worth considering triple on some windows (e.g on north walls) and good double on the rest? Again, open to suggestions and experiences.

As far as BER rating goes, we are not going to be overly concerned, as we are building this house to live in & not to sell on.

We would also appreciate advice / opinions on build costs – our research suggests that building a passive house is around 15 - 20% more expensive than building the traditional way – is that people’s experience?

Apologies for the long thread but we would really like real-world experiences before we start properly. Many thanks, & we look forward to hearing from you.

BryanF

look up the passive house website and pick a phpp designer/ arch your happy to work with. Interview several and look at examples.
Read around the forum, use the search function, all of the above questions are answered.

RKQ

Its great that you are considering passive house standards. It is a very high standard and well worth exploring.

From experience, IMO installation of air tight membranes, external ope details, roof details especially at eaves are very important. It is important to use experienced installer / sub-contractors or Builders. The old FAS ran a number of courses for carpenters etc on installing membranes etc.

HRV systems are very important and necessary in a passive standard air tight house. The systems with washable filters seem to be the most popular.

I have engineered oak flooring on UFH with a geothermal heat pump. The oak is fine, nice and warm and never warper in 10 years.

Do your homework, it will pay off in the end.

CiaraG75

@Bryan F - thank you; have seen lots on here, but really looking for the most up-to-date experiences & opinions. Will definitely dig deeper into the people registered through the passive house website.

@RKQ - thank you; would be interested in your opinions / experience of the geothermal system if you have the time. Do you think it is worth the initial outlay? What is your experience of installation? Commissioning? Working as a system? Do you know what the going rate is at the moment? We haven't really done any research into geothermal yet, but intend to....

fclauson

my view UFH is perfect for a passive house - rads just take up wall space

get away from the 2hs in the morning 2hrs in the evening heating cycle - mine is on 24hrs with no thermostats - its intelligence works out when to add heat

total h/w and heating was 4000Kwhs of electricity

CiaraG75

@fclauson - thank you for your reply. The reason we were thinking of radiators upstairs was that the space needed between floor and ceiling for the HRV ducts is too much to put in a concrete floor upstairs - and no concrete floor upstairs means no UFH upstairs. Would that be your experience?

BryanF

CiaraG75 wrote: »

@fclauson - thank you for your reply. The reason we were thinking of radiators upstairs was that the space needed between floor and ceiling for the HRV ducts is too much to put in a concrete floor upstairs - and no concrete floor upstairs means no UFH upstairs. Would that be your experience?

Ciara, your post is typical of what many suffer from when starting on the 'new house road'
Don't get hung up on the detail just yet. Get a design done first by someone who knows what their talking about.
Do the phpp before submitting planning.
To answer your question, you simply use a suspended ceiling or clever design to hide ducts when concrete first floor is your preference

galwaytt

I can help on the UFH heating angle: ....there's no reason why you can't have UFH, with concrete screed and MHRV in a timber framed house - I do. And I know many others that do as well.

15% - 20% is a good rule of thumb for the premium for a passive-certified build.

No6

Ciara

For a certified passive house you will need a design which has been modeled using the phpp software by a certified passive house designer.

here is the link to the Passive house designers http://www.passivhausplaner.eu find one as they will be able to guide you.

The theory behind passive houses is that you use a high thermally efficient building envelope with minimal air movement which reduces your heating requirements to a level where you can dispense with wet heating systems and expensive ones like geothermal.

beyondpassive

Passivhaus.

You have to comply with the building regulations. Otherwise its illegal to occupy the house. You wlll be also now subject to building control. What that essentially means is that you need to build a house that uses 60% less energy than a house built up to 2009.


Costs for the extra energy improvements are 4-9% according to a paper I researched last year. This cost is down to extra time and materials for airtightness and some slight improvements for windows and Ventilation. In general these houses cost 20% more than your common one off, mock georgian because the design input and finishes are of a much higher quality.

For a Part L 2011 compliant house you will most likely have the same levels of insulation, similar windows, you will have MHRV and renewables based heating system. If your house is Architectural designed rather than by a planning practitioner, you will have a higher glazing ratio to maximise light and views The higher the glazing ration, the higher performance the windows, doors and rooflights. What you really pay extra for in a Passivhaus is workmanship and quality control. With rigourous testing, there is nowhere to hide for shoddy work.

For heating, we generally see Underfloor downstairs and rads upstairs, Gas or LPG boiler with solar tubes with an accumulator and a room sealed stove. Alternatively, Air sourse and PV or Geothermal heatpump. The underfloor and internal concrete works like a storage heater, so very little fluctuations in temp and humidity to affect your timber. Wall systems are EWIS, wide cavity or Vapour diffuse Timber frame wrapped in a sarking board. Windows are class 4 airtighness non-thermally broken Aluclad with 3G.

The biggest saving you can make is in the design, compact and solar optimised. Streamlined and sharp is good, fussy and fake historic is bad. Dont listen to a designer that tell you that the house has to have a farmhouse front elevation, thats not design.

Greenair

Ciara
We are currently coming to the end of a certified passively build in Glenfarne , Co Leitrim. Would be happy to advise, show you round .