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Community and Q&A

PassivHaus backyard workshop

CalBungMelb | Posted in PassivHaus on

We’re looking to build two sheds in our backyard. One is for storage of lawn-mowers etc and doesn’t need to be insulated. The 2nd will be a workshop in which we will probably spend a reasonable amount of time. We’re keen to do this as a sustainable showpiece highlighting various aspects of sustainability. We have thought of doing it as a PassivHaus project. As far as I know there are no complete, stand-alone PassivHaus buildings in Australia so this might be a useful demonstration site. A few things come to mind that perhaps some GBA folks could comment on.

We’re planning to either build on a concrete slab or stumps. If we use stumps would this complicate insulation? I was thinking that we could have the floor nice and sealed even if there was a space underneath. We plan to have cladding going down to the ground which will minimise airflow around the floor.

As one aim of the workshop is to have some woodworking gear we will need to have extractor fans and ducts that will pass through the wall(s). I guess this might complicate getting good thermal performance?

The climate in Melbourne is roughly Mediterranean with temperatures sometimes getting down to 0C in winter. We had one day a few years ago where it was 46C but generally its milder in summer. So we don’t have the very cold conditions of northern America or Europe but we might need a bit of active cooling in summer; particularly if we’re running machinery.



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  1. GBA Editor
    Martin Holladay | | #1

    First, allow me to be somewhat curmudgeonly: if you are building a backyard workshop in a Mediterranean climate, and if your aim is "sustainability," then I strongly suspect that your attempt to comply with the Passivhaus standard will be a waste of resources. I don't think that you need to aim for 0.6 air changes per hour @50 pascals for such a structure, nor do I believe that Passivhaus levels of insulation are required. You may end up spending more on windows, insulation, and air sealing tapes than the building deserves... so how is that "sustainable"?

    Now that we have that out of the way: you can build a Passivhaus building on a concrete slab if you want, or on "stumps" (we would say "posts" or "piers" in North America). For more information on slab foundations and pier foundations, see the relevant articles in the GBA Encyclopedia:

    Slab Foundations

    Pier Foundations

    If you choose a pier foundation, you need to come up with a detail to avoid thermal bridging through the piers. One way to do this is to use a SIP floor. Here are links to two websites with information on SIP floors:

    SIP floors from Premier SIPS

    SIP floors from Extreme Panel Technologies

    You are quite right about exhaust fans. If you have a workshop with continuously running exhaust fans, it's going to be hard to meet the energy limits established by the Passivhaus standard. That's one more reason to conclude that aiming for the Passivhaus standard may not make much sense for the type of building project you envision.

  2. CalBungMelb | | #2

    Thanks for the information on using slabs and piers, Martin. Re your comments on fans, we wouldn't be running the fans continuously. I was more concerned about the thermal bridges introduced by the ducts.

    As for the curmudgeonly bit, I guess important factors are what is the extra cost for using a PassivHaus approach beyond what we would spend anyway and what benefits we would achieve for this cost increment. Also relevant is if a PassivHaus approach would use significantly more in the way of inputs such as embodied energy.

    I toured a number of Near Zero Energy buildings in Wels earlier this year. Many of these buildings were PassivHaus. A representative of the local council told the group that they were focused on using materials that not only gave the desired thermal performance but also met other sustainability criteria such as low embodied energy. It would appear that these other objectives can be met



  3. Expert Member

    David, Many of us elsewhere look to the work of Australian architects such as Glenn Murcutt for examples of how to build structures appropriate to specific climates in an environmentally sound way. If I was building in Melbourne I'd think about adopting their approach over the prescriptive demands of Passivhaus, which is probably more appropriate to Northern Europe than the Antipodes.

  4. CalBungMelb | | #4

    Thanks, Malcolm.

    There seems to be quite a bit of interest in PassivHaus in Mediterranean climates in the Northern Hemisphere. And some analysis of how this might go locally. For example:

    Local energy efficient houses like this one (which is in Melbourne's northern suburbs):

    use many of the features familiar to the PassivHaus community. The builder says in the comment at the end of the article that it would be close to PassivHaus standards.

  5. user-757117 | | #5

    I don't disagree that the PH standard is something to think about for a home, but it's not clear to me that there is anything to be gained from building a workshop this way.

    I think Martin makes some good points.

    The extra insulation, supplies and high-quality windows required to meet the PH standard represent both a possible excess commitment of material as well as a greater component of embodied energy than would otherwise be.

    Except for plug loads, the shop's energy footprint should be pretty low already from only part-time occupation...
    Sounds like you'll only be conditioning the building on some of the hotter days of the summer, and even then that will probably only be part-time...
    Why bother with the PH standard in this case?

  6. CalBungMelb | | #6

    Well, Lucas, I guess part of the project would be to show the benefits :)

    We're aiming to use low embodied energy materials. I'm going up to a farm100km north of Melbourne tomorrow to look at what they have in the way of windthrow timber that I can mill onsite to use for the cladding, stumps and maybe framing. And also possibly shingles for the roof. (Just for extra cred I'm having a crack at riving some of the wood for the cladding. Although I have no idea how well this will turn out.) Most of the building will be timber. At the moment we're planning cellulose or sheep wool insulation.

    I've found a local supplier of good quality timber framed double glazed windows. There would be some increased embodied energy over single glazing.

    A good quality design and build that is aesthetically pleasing, adds value to our property, uses little to no energy for heating and cooling and is pleasant to work in is an appealing prospect.

  7. GBA Editor
    Martin Holladay | | #7

    Your materials choices all make sense for someone who wants to build a structure with local materials. So that's good.

    However, I'm not sure that the Passivhaus standard is appropriate for the type of building you are planning.

    To be green, one needn't comply with Passivhaus.

  8. Expert Member

    My concern is that there is that while many useful and interesting advances in energy efficiency is occurring in communities such as Passivhaus, a disconnect is occurring between their aims and the larger concerns of domestic architecture. Living in a hermetically sealed structure may be appropriate to extreme northern climates where houses have historically has to be enclosed to keep out the harsh elements, but in more temperate zones a more fluid division of inside and outside has always been the norm. This makes good sense for energy reasons too. The summer kitchens of early American houses, root cellars, covered porches and many other features all reduce heating and cooling loads while providing comfortable living spaces. But this approach also has social consequences. Another version of the hermetically sealed box is the air conditioned house that residents of places like Las Vegas retreat to. Wildly inappropriate to the climate and unlike the indigenous architecture found in all tropical countries, Adopting these approaches makes it difficult to create a meaningful relationship with the nature that surrounds the house, and precludes the creation of many of the common spaces that form the backbone of social interaction in communities. It isn't coincidence that most passivehouses look like they have been seeded from spaceships with no regard to their surroundings. My question would be is that an appropriate prototype to introduce to Australia?

  9. GBA Editor
    Martin Holladay | | #9

    If you are growing bananas -- you don't need Passivhaus!

  10. CalBungMelb | | #10

    Martin and Malcolm,

    All good points. And if we go ahead with a PH or PH influenced design no doubt these issues will come up in local discussion as well as on GBA.

    Totally agree, Martin, that you don't have to be PH to be green. But an existing, well-defined technology stack that will deliver what we want is attractive. It means that we can work with suppliers, local council planners, designers, architects etc in a referenced framework which will reduce the time and effort required for the project. We would already be pushing the envelope a bit with a PH design. I did think about solutions like mud-brick (be nice to get some benefit other than excellent potatoes from all that clay), strawbale, rammed earth, earthship etc (we did a small amount of work on an earthship a few months ago; fascinating technology) but for one reason or another these may not be as well suited to our place. I toyed with the idea of making the roof using joinery and wooden pegs. But one of my nephews works at a place that makes roof-trusses which means that I can get these at a good price. And I've been giving some friends a hand with building a reasonable sized timber deck. The builder for the deck was interested in the idea of using joinery for the shed-roof but emphasised the ease and time-savings of using gang nails and standard truss construction. And he's right. The frames of many of the houses in Melbourne used to be built using green (as in not kiln-dried or seasoned) native timbers. Local builders had developed a bunch of techniques to deal with movement in the timber as it dried. I had thought of using this approach for the shed using local urban salvaged timbers. But the very experienced builder who ran the framing course I did last year while recognising that it was possible to use green timber for the frame and get a good outcome gave a number of very good reasons as to why not. So we'll use kiln-dried/seasoned wood.

    You raise some interesting points, Malcolm. If you saw our back and front yards I think you might say there was a fairly substantial connection with the surrounding environment. We have a sizeable number of fruit and nut trees and bushes, canes, vegetable beds, ornamentals and natives. Judging by the enthusiastic participation of the native birds and mammals in helping us at harvest time they thoroughly approve of this project. And I wouldn't have thought that rainbow lorikeets liked eating apricot leaves but that appears to be the case. As an aside, this probably isn't good from a climate change perspective but we also have our first bananas forming. Melbourne has generally been seen as right on the edge of viability for bananas to fruit outdoors and to achieve this usually took a warm micro-climate garden position. We know of quite a few people who have succeeded in the last few years. Our banana stems are just out in the backyard with no particular micro-climate consideration.

    Back to energy efficient structures in Med climates. We are visually referencing traditional Australian shedding designs with the use of timber cladding. And we will probably use either corrugated iron or timber shingles for the roof. I don't think what we build will look overtly modern or out of place in that respect. We're in a heritage overlay area so this is a design element we need to keep in mind.

    We would plan to keep windows and doors open to make use of ambient temperatures and night purging when appropriate. As to the use of this technology as against passive ventilation etc approaches, I wonder if folks in earlier times in Med climates would have used cost-effective energy efficient technologies a la PH if they had have been available.

    All good stuff!


  11. Mike Eliason | | #11

    a few thoughts...

    1. murcutt is a great example of architecture rooted in place and climate. however, his projects wouldn't be as adequate performance-wise for 80%+ of the u.s. frankly, most of his projects wouldn't meet our energy codes. but boy are they phenomenal.

    2. for much of australia, little insulation would be required, double-pane windows would be adequate. the 'upcharge' to PH would be significantly less than in most US climates. i believe even the PHI has stated that in warmer climates the airtightness can be loosened.

    3. passivhaus buildings look no more or no less different than the other 90% of the built environment. in fact, despite the absurd comment above, most PH projects look exactly like their non-PH neighbors and most folks couldn't point out which was which.
    spot the passivhaus!

    that being said, i don't think shooting for PH on a shed makes any sense whatsoever.

  12. CalBungMelb | | #12

    This area certainly seems to attract some strong opinions.

    I agree with Mike that doing PH for a garden shed wouldn't be appropriate. That's why I made a point of saying that we wouldn't worry about insulation etc for our garden storage shed.

    But it's a different story for a workshop/studio. We'll have equipment in there that will have some temperature sensitivity, we'll spend long hours in there at times, we'll be doing cognitive and manual work that requires focus ... I'm a bit surprised that a comfortable, cost-effective, energy efficient environment for this would seem anything but desirable. What's it worth to avoid messing up a design or an injury from a tool because you were hot?

    My wife's father is a very handy fellow. After retiring as an engineer, to keep himself occupied, amongst other projects he has built sit on, steam engine powered scale trains from the ground up, so to speak, including turning the pistons from block metal. (He just sold one for $10k which was a bit of an eye-opener.) He can't work in his workshop during summer as it get too hot.

    To me it makes sense to have a space that is usable at all times of the year with little energy use achieved cost-effectively.

    And if we build it well it can always be converted to other uses down the track once we cark it.

    Anyway, I guess part of the project would be to examine alternatives and to record why various design and build paths were taken.



  13. GBA Editor
    Martin Holladay | | #13

    You write that one of your goals for your construction project is that the specifications be "cost-effective."

    It is precisely this question -- the question of cost effectiveness -- that leads some of us to doubt whether you should be pursuing Passivhaus.

    In your climate, it is highly unlikely that a desire for cost-effective comfort in a backyard workshop has anything to do with the Passivhaus standard.

  14. homedesign | | #14

    I think it depends on how often this "backyard shed" is occupied.
    If it is only a few hours a year... or a few hours a week then it does not make sense to go to extreme efforts.
    If it is occupied 40 hours plus a week....hmmm

    I admit that I do not know your climate....
    A Mediterranean Like Climate is not exactly "paradise"....and 115 degrees F is not-so-wonderful.
    Martin and some of the other Cold Climatists have little sympathy for people who live where bannanas might be grown.
    Passivhaus is being considered for the Mediterranean climate
    quote from the webpage:"Contrary to some publications, good thermal protection also helps to provide high thermal comfort in summer "

    Is a Passivhaus or a PassivArbeitzplatz in Melbourne really a ridiculous idea?

  15. homedesign | | #15

    Albert, you (and Vitruvius) are right about "delight"

  16. albertrooks | | #16


    Go for it. I think that everyone is missing the point of "experimentation".

    John Brooks: I think it comes back to another case of "delight" as the double stud Gambrel was. And... Thanks for posting the PH Med study. We just added that book to stock this week (I haven't even finished the descriptions yet) and I started pulling notes out of it last night for this thread but got waylaid.

    David: The envelope demands for a Mediterranean climate aren't really that extreme at all. Here are the findings of the 2009 study (that John posted) done by Jugen Schieders of the PassivHaus Institut on creating Passivhauses in the Southwestern Europe Mediterranean climate:

    The 337 page study studies creating the PH energy balance in 12 locations ranging across the Iberian peninsula of Portugal & Spain, both northern and souther Italy and coastal France. Look for the red dots on the cover photo below.

    A few quick highlights of the study are:

    "Double low e glazing with a noble gas is usually an appropriate choice. Triple glazing often has no thermal advantages"

    "Good movable exterior shading is indispensable. Without movable shading the cooling load can increase by 5W/m2."

    "The use of night ventilation (from tilted windows for example) can reduce the cooling demand to good wall insulation or heat recovery bypass."

    "Excellent airtightness reduces the heating load in all climates."

    "Another essential feature is good thermal protection. High insulation levels are a prerequisite for low heating demands."

    "The installation of supply and exhaust air ventilation systems turned out to be important in most locations for different reasons."

    "Thermal mass is useful but of less importance."

    "The avoidance of thermal bridges is not quite as essential as in Central Europe"

    "In the hottest climates, the insulation of the basement ceiling, or the slab is not advisable. Instead, the small heat flow into the ground reduces the sensible cooling demand in the summer and can easily be compensated for in the winter." In the cooler locations an insulation thickness of 10 to 15 cm (4 to 6 inches) is appropriate,"

    The study quoted insulation levels at 10 to 20 cm (4 to 8 inches) depending on location. All of this sounds fairly reasonable to me when the outcome is creating a comfortable building or workshop with an energy balance less than 15kw/m2. One of the more interesting quotes in the study was that the envelope needs were moderate compared to a norther climate viewpoint, and that modeling the building was more "tricky" than building it.

    I like the idea of a demonstration project. It will become quickly apparent what you have available to work with in windows and airsealing materials. The window issue could be more challenging than airsealing due to how good the local windows are sealed and how conductive the frames are.

    The rest of the issues seem small: Moderate insulation quantities, no sub-slab foam (the quantity of which can be a point of contention with Martin and the PH "extremist" :-) ) and reasonable ventilation. Working out the exterior movable shading will be interesting.

    The value of the demonstration project is finding the regional obstacles and then working on the solutions. I think you're doing your region a great service by taking on the project and seeing what the difficulties are.

    From the point of view of the US Pacific Northwest, our first completed project in Seattle was a 300 ft2 ADU by Joe Giampietro. That's quite small and Joe wasn't planning on living in it. He just flat out wanted to build it. He did, and it worked. The rest of us learned a lot from it.

    Good luck to you David!

  17. CalBungMelb | | #17

    Thank you Albert! Your post was very informative and I appreciate your positive sentiments.

    You raise a number of points:

    a/ Exterior shading. The traditional approach to seasonal exterior shading is to plant a grape pergola or to use deciduous trees. The site where we're thinking of putting the workshop would have the building east-west oriented with an existing shed on the northern boundary (next door) and another shed to the west (converted garage on our place.) Remembering this is southern hemisphere we are shaded (but fixed shading) to some extent already. This would help restrict solar gain in summer but does mean that we will have limited direct sunlight in winter. The main summer sun exposure wuld be on the roof. I guess modeling could help to decide how the roof should be constructed. We could possibly build a grape pergola over the roof of the building.

    b/ It sounds like we're not going to need the level of stuff needed to achieve PH in colder climates. I thought this would be the case but it's great to have this confirmed. This will of course have a beneficial effect on the budget.

    c/ An interesting design consideration is how we can integrate the timber we want to use with the thermal and air-loss performance goals. I've attached a photo I took at the Agrarbildungszentrum (Agricultural Education Centre), located at Altm√ľnster in the Salzkammergut region of Austria on a site visit earlier this year. That's a lot of layers! If we have interior wood paneling and floor and exterior timber cladding how much this can be part of the thermal performance and air-loss capability will be of interest.

    d/ Ventilation will require some thought. There are some small HRV systems that we could use. But these are a cost and we would prefer to use passive systems if possible. If there are times that we don't use the workshop for a period we don't want the interior air to build up moisture. Perhaps a small window opening and closing depending on exterior and interior conditions might be a solution.

    All good fun!


  18. Expert Member
    MALCOLM TAYLOR | | #18

    David, your responses to a diverse range of comments all speak to there bing a very good chance this is going to be a thoughtful and interesting project. Good luck!

    Mike wrote:
    "murcutt is a great example of architecture rooted in place and climate. however, his projects wouldn't be as adequate performance-wise for 80%+ of the u.s. frankly, most of his projects wouldn't meet our energy codes. but boy are they phenomenal."

    I agree they are not transferrable. What I think is useful is to choose a starting point which is as you say rooted in a particular place, then see what works, not start with a prescriptive approach such as Passivhaus.

    While I may not be able to distinguish the Passive-houses from their neighbours, I would also because of their generic nature have difficulty knowing where in the world they were located. Not something you could say about Murcutt's work, or many others rooted in "place" that respond to their immediate contexts.
    Again, having read David's responses I don't think this is half the issue I first assumed it o be.

  19. CalBungMelb | | #19

    Probably time to pull together the strands in this thread.

    John: The PassivArbeitplatz project; love it! I've been using "Sustainable Shed" as the project name and had considered the Banana Studio given the interest in this thread thereof. PAP can get things started.

    Re the bananas. They're a cool climate cultivar supposedly bred to fruit this far south. Remember there's nothing between us and Antarctica but the windy waters of Bass Strait, Tasmania and thousands of kilometres of Southern Ocean. We haven't changed to a sub-tropical climate as exists in places where bananas are more commonly grown such as Coffs Harbour on the northern NSW coast. It will be interesting to see if the fruit ripen up properly. The plant needs to do a lot of photosynthesis to make all those carbohydrates.

    Re the main point of objection to using PH for a studio which appears to be the cost-effectiveness. I'm doing a research project at the moment where I'm looking at the Levelised Cost of Energy of various forms of renewable energy. Using a similar time value of money calculation with an appropriate discount rate I could look at annual energy saved against initial investment and annual operations and maintenance costs. And some sensitivity analysis could be applied to projected energy costs.

    Establishing what would be the Business As Usual (BAU) case and associated costs would require some care. The BAU is required to allow calculation of the cost increment for the PH structure.

    But this should be doable.

    More problematic is that the PH structure would be by definition something of an experiment so this makes it difficult to allocate what would be the costs if this were a widely used standard approach. But we will see what comes out in the wash. It sounds like there's some useful science to be done.



  20. user-757117 | | #20

    I'm not trying to rain on your parade.
    But I'm not sure this is quite right:

    Re the main point of objection to using PH for a studio which appears to be the cost-effectiveness.

    Personally, my point of objection has more to do with the idea of conservation of resources.

    The PH standard is at its core a prescription for a very low-energy enclosure.
    Generally speaking, you don't need a very low-energy enclosure if you are using very little energy to begin with (ie, the shop is unoccupied and unconditioned most of the time).
    What isn't clear is how often your shop would actually be in use - and how often the HVAC would actually be used.

    You may want to try to get an annualized estimate of what your cooling energy and total source energy requirements might be for a "code compliant" enclosure, factoring in actual usage.
    Since it is not a home you are building, it is possible that on a meaningful number of days per year your shop could be using no energy at all.
    If you're anywhere near the vicinity of the PH maximums using a "code compliant" enclosure, then building to a higher standard might not be the wisest use of resources.

  21. CalBungMelb | | #21

    I guess we'll have to see what the design modeling and experience in the completed structure shows regarding cooling needs, Lucas. And I don't think I could have emphasised more that we are shooting for low embodied energy materials.

    On that topic I spent an enjoyable Saturday tussling with chainsaws and obdurate timber. The windthrow turned out to be a mixture of Red Box, Grey Box and Ironbark. All absolutely superb timbers with Class 1 below ground durability and high hardness ratings.

    Riving and shingle making? Forget it. The Red Box (Eucalyptus polyanthemos) I worked with had been burnt in a fire some years ago and cut down by the farmer as it was next to a track. It had coppiced exuberantly with a large number of new stems. But it had dried out quite a bit and wasn't going to accept a froe or wedges belted with a sledge hammer.

    And some research post-visit once I knew the species indicates the grain of this timber is probably unsuitable for riving.

    But there's a few trees that could be utilised. Red Box is a very attractive timber with a lovely grain and pink appearance. It might be used for stumps, cladding, paneling or flooring. Just a matter of whether I can mill it with my limited skills and equipment and how much timber can be salvaged from this site.


  22. user-757117 | | #22

    And I don't think I could have emphasised more that we are shooting for low embodied energy materials.

    Fair enough.
    But using less of the same materials will always result in lower total embodied energy.

    Your interest in creating a demonstration project is admirable.
    Given the recent energy audit you had posted on, have you considered a PH retrofit of your home?

  23. CalBungMelb | | #23

    We have been considering a small extension at the back of our house. If we do this we will investigate cross-laminated-timber (CLT) and use PH approaches. The world's tallest timber building at 10 storeys has just gone up in Melbourne. CLT appears to be a viable option for domestic construction as well.

    As for a PH retrofit of the existing structure. I've spoken to a few people about this. My understanding is that this is difficult without fairly major surgery. We will certainly aim to increase the thermal performance substantially without attempting formal PH certification

  24. kevin_in_denver | | #24

    A slick foundation system for a workshop is at:

    Very quick, easy, and cheap. A SIP floor may be required, as Martin said.

  25. CalBungMelb | | #25

    So the project kicks off tomorrow with a builder coming around to have a chat about what's involved. He doesn't have any experience with PassivHaus building but he's been recommended by a sparkie I've been doing some renewable energy work with as someone who has a great deal of enthusiasm for energy efficient building. Which is a good start. I've emphasised to him that we want to shoot for PassivHaus and we have a preference for timber.

    If anyone has any links to documents, blogs etc for how to tackle PassivHaus construction with builders new to the technique pleased pass them on



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