A post about Passive Houses – Passive House

Following last weeks Grand Designs Stealth/Passive House (HERE’S THE LINK TO CHANNEL 4 PAGE) I thought I’d contribute to the discussion:

First of all let’s get out of the way my opinion of the house; of course I liked it, how could I not when we are living under ground in our own house (bare concrete, exposed structure…) (HERE’S A LINK TO OUR UNDERGROUND AREA). The purpose of this post is to give a little more information to anyone interested in having their own passive house.

First of all it’s important to differentiate the difference between a Passive House and a certified Passiv Haus; The Passivhaus Standard is a construction standard developed by the Passivhaus Institut in Germany. The Passivhaus Standard is a specific construction standard and if your house meets that standard can be certified as an ‘official’ and ‘certified’ ‘Passive House’.

So what is a Passive House ?:

A Passive House is so well insulated, the annual space heat demand is so low that a conventional heating system can be omitted. The threshold for this to happen therefore is a space heating energy demand of up to 15 kWh/(m2a).

How is a Passive House Measured ?

A house meets the Passive House standards (incidentally any building, not just houses can also be certified by the Passive Haus Institute) by a thorough analysis using the PHPP software. The PHPP software takes the following into account:

* Building dimensions & orientation
* U-values for all elements including windows, doors etc…
* Thermal bridges
* Shading
* Window orientation
* Ventilation
* Climate
* Domestic hot water heat demand
* Solar domestic hot water
* Electricity
* Boilers


The performance requirements for Passive Houses are detailed below. It is important to note that it is not any individual value as it is the total house that is calculated as a whole and you are allowed to use components with less strict values, as long as you meet the overall performance requirements:

1. Total heating and cooling demand smaller than 15 kWh/m²
2. Total primary energy demand smaller than 120 kWh/(m²a) including ALL energy consumed (incl. household electricity e.g.)
3. U value of exterior building elements below 0.15 W/(m2K)
4. Constructed without thermal bridges
5. Air tightness of 0.6ac or better (N50 not Q50) at 50 Pascal
6. U value of all glazing below 0.8 W/(m2K)
7. Very high energy recovery efficiency ventilation system (>/ 75% complying with PHI certification) and minimal electricity consumption (</ 0.45 Wh/m3)
8. Minimal heat losses to hot water generation and distribution
9. Highly efficient use of electricity


As well as fulfilling the above (and proved through the PHPP software) you will also need to provide:

* Full drawings that include any shadow casting objects (trees etc…); this would involve site plans, construction drawings, detail drawings, window locations (to ascertain thermal bridges), M/E drawings…

* Technical Specifications for:

– Window/door frames
– Glazing
– Services
– Components
– Electrical components (household appliances etc…)

* Declaration of construction supervisor

* Photographs throughout entire construction process showing every element

I've condensed this down to be readable but if you think there's something unbelieveably important – let me know and I'll include it.

You are then ready for your house to be inspected and verified by a Passiv Haus certified inspector (a fee of a few thousand € from memory).

The above information is also available as a downloadable pdf fact sheet

I have two projects currently in planning that are being modelled using the PHPP software and hopefully will go forward to be certified, so watch this space…

If you are interested in a Passive House (whether certified or not), please do not hesitate to contact me:

Mark Stephens RIBA MRIAI, Passive house PHPP architect

0 thoughts on “A post about Passive Houses – Passive House

  1. I would call the specific values of components (U-value wall, heat recovery etc.) “recommendations for Central European Climate”, not requirements. You are allowed to use components with less strict values, as long as you meet the overall performance requirements.

    These performance requirements for Passive Houses are:
    (1) total heating demand smaller than 15 kWh/m² (living area), calculated by PHPP using the regional climate
    (1a) total cooling demand also smaller tahn 15 kWh/m²/a
    (2) airtightness better than n50 of 0,6 h-1
    (3) total primary energy damnd smaller than 120 kWh/(m²a) including ALL energy consumed (incl. household electricity e.g.)

    Good success with the projects.

  2. Mark,

    I have built a certified Sub-10 Passive House for a private client in Ireland. That is 50% better than the Passive House 15kW/m2K standard and has a wall thickness of only 305mm. Ireland is the cheapest place in Europe to achieve the PH certification because our climate is made for the passive house.

    I would encourage all architects to go for PH certification because “near Passive” is a recipe for being sued in the future.

    PH is a holistic approach that deals for the first time with the very serious issue of interstitial condensation cause by linear thermal bridging. Up to now we have only survived as a profession because we had such leaky houses. Just cutting out draughts means lower air quality and much greater condensation within the construction. Just adding insulation actually increases the vulnerability of those linear thermal bridges: the more insulation you add the worse the hidden condensation issue becomes. In our climate, that is a recipe for decay.

    It may take 10 years to evolve, but my prediction is that “near Passive” will become the actuarial equivalent of “smoker” or “downhill skier” to a future household insurance provider.

    Already it is more expensive to insure a timber framed house – in future it will be impossible to insure a “near Passive” house. A certified Passive House will not face the same problems because they will not need to be rebuilt due to structural decay.

    My advice is to build it right first time. The cost difference is negligible, in fact, given my experience with the Sub-10 house, I am convinced that I can build a 3-bed detached to certified PH standard for LESS than a traditionally built, building regs compliant, house. That represents a CO2 emissions reduction of something like 90% over the full lifetime of the house. Zero carbon and energy positive are merely a bolt-on piece of kit away when ever the client wants to add them.

    Why would you build anything else?


  3. Don’t forget Mark that the Schroder house was designed by a cabinetmaker and there are many architect-designed houses that would be embarassed in its company. Training is often an inadequate substitute for ability.

    Good design does not gaurantee good building, however much we kid ourselves. If it did, there wouldn’t be half the number of claims against architects p.i. insurance. We need to build competently whatever design our skill and our clients budgets allow. With the new energy performance demands, that is far from a simple task.

    The good news is that achieving compliance is now well beyond the competence of the self-builder so more of our houses will be designed by architects.

  4. Hi all – just came across this thread, whilst ‘on a google’ for something else !

    If I may, I feel the comment ‘The good news is that achieving compliance is now well beyond the competence of the self-builder so more of our houses will be designed by architects.’ is a bit premature.

    As surely as the posts above mention the climate of PI claims against architects, so too the practice – of practicing – to building Passive performance houses is, in fact going to be an evolution, not revolution – and there will be mistakes along the way.

    And, similarly, as surely as the complimented-upon Schroder house is acknowledged as good, but not by an architect……….then somewhere out there is a similar ‘non-expert’ is going to appear in the PH field………it would be brash to assume otherwise……….

  5. If i understand it correctly, I disagree with John Moylan’s “evolution” suggestion – Passive House is so far ahead of current practice in Ireland (or anywhere else) that adopting it cannot be considered other than revolutionary. I accept that once the certified – and I mean only certified – Passive Houses gain traction, there will be a subsequent evolutionary progress towards sub-Passive, like my own Sub-10 Passive house (see ConstructIreland Feb 2011).

    The difficulty arises in the evolution of the “near passive” status where all sorts of dodgy experiment at the expense of clients is taking place often as a result of a fundamental misunderstanding of the passive house concept. Aiming for a “near passive” house is an invitation to failure – it will be the “near passive” houses that end up in court or the subject of claims against PI cover. The certified Passive House incorporates checks and balances that ensure the elimination of key areas of potential failure like linear thermal breaks, internal air quality and interstitial condensation. The “near-passive” house designer often has no conception of the serious risks it they are playing around with in these areas.

    It is lamentable that the trajectory of Irish Build Regulations is towards an ill-defined “near passive” status by 2016, precisely the territory where most failure will occur. In my view this is irresponsible and a major disservice to Irish consumers. We should be legislating for beyond certified Passive, if not for reasons of national energy sovereignty, then simply as a consumer protection measure.

    There are already at least three Sub-10 passive houses in Ireland and almost none anywhere else. That is evidence of evolution beyond the revolution, or, more accurately, evolution on the safe side of the revolution.

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