The 100K House project gets passive

Written by adam


A few months ago I wrote about the 100K House, a project to build a LEED-platinum certified home for $100,000 in construction costs. The developers, a company called Postgreen, are continuing in their quest for world domination, and their next batch of urban homes will be built to the even more exacting Passive House standard.

Passive Houses, you may recall, are constructed with an airtight envelope and ultrathick insulation. They use mechanical ventilators to draw in fresh air, with heat exchangers to ensure that a minimum of energy is lost to the outside. Passive Houses are so thermally efficient that they require barely any heating or cooling, even in the harsh central European climates where they were first developed. A Passive House uses about 90% less energy than a conventional home, and their small energy load can often be supplied by on-site renewable generation, making them Zero Energy Homes as well.

I had the opportunity to tour the original 100K House while on a recent trip to Philadelphia. In addition to its low energy footprint, it comes with some other nice green amenities, including solar hot water heating, a convection range, and a combination washer/dryer unit that doesn’t require a vent because it uses a condenser to reclaim water.

Postgreen been successful in meeting their goal of green and cheap because they’ve taken a whole-systems approach to house design. Their homes are smaller, use load-bearing prefabricated insulated panels as the primary construction material, and employ an open floor plan that is easier to heat and cool. The modernist design isn’t for everyone, but the homes are finding a ready market, even in the current recession.

For decades, home buyers have been conditioned to think of their house an an investment, something that can only climb in value. With this mindset, buyers seek to maximize the amount of money they spend — to take out the biggest possible mortgage — on the theory that more money put in means even greater appreciation.

Postgreen anticipates that people will begin to see their homes as they really are — not just an investment but also as an expense. Buyers will seek out not just the best investment, but also the best deal: homes that radically slash their energy budgets while still offering modern amenities at affordable prices.

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  1. Jeff Carpenter

    Convince me of the benefits of a flat roof–yes, a garden may be planted; but in “harsh Northern climates” will rain/snow be problematic on a flat roof?
    Otherwise, kudos for the efforts and the design; perhaps the regeneration of the housing industry will begin when a brave contractor or two is sold on the design, when community planners boldly promotes “green” as a lifestyle instead of “style”—keep such efforts in the public’s awareness.

  2. Angie K.

    I agree with Jeff that flat roofs are usually a problem. Not only in areas with heavy snow, they are also a problem in areas with heavy rains, like Florida. I also wonder why energy efficient design also seem to lean toward boxy styling. I’m sure that a little more character could be added for little money. Perhaps, if we had a community model for building these types of homes similar to Habitat Homes, style would not need to be sacrificed for cost savings. Generally, labor is one of the greatest expenses.

  3. Ed

    I’d heard (mostly from the popular press—NYT did a big feature on passive homes about 6 months ago) that the catch was cooling the house in the summer. Sure it’s easy (relatively speaking) to capture passive heat from cooking, human bodies and light coming in through the window, but there’s no passive way of cooling the house in the summer (an issue in most of the US — particularly the high-growth sunbelt). Is that no longer the case?

  4. Brian

    You see flat roofs in northern cities like Boston all the time. If they’re done right, they work fine. A flat roof still has a slight slope. Snow load has to be taken into account when designing the structure.
    I think the passive concept is excellent. Mechanical heat is expensive and the technology is there for warm-air exchange so why not use it. I think the issue of cooling might be partially solved by shading windows on the south side with awnings, strategically planting trees, and designing skylights that open that use convectional air currents to suck warm air up and out.
    As far as aesthetics, I bet with the right trees and landscaping, it’s a non-issue. The owner can always re-factor and change the facade when they have the money. This is a great cookie-cutter way to help solve the global warming crisis. Let’s get these built! 🙂

  5. Chad Ludeman

    Thanks for the great post. I thought I’d try to help clarify a couple of the questions. One, we are building, not selling, the original home for $100K. The new Passive Project has a slightly higher build budget, but we are still aiming to beat the $100 psf construction cost.
    Two, the boxy design and flat roof is mainly due to the infill rowhome condition in Philadelphia. Pretty much all homes have flat roof with torch down rubber that come with 15-30 yr warranties. All homes are also sharing party walls, so they can come out a bit boxy.
    Having said that, we have an intentional modern aesthetic that avoids extra traditional details that don’t add value to the homes. Also, any cantilever or bay window, which is very popular in traditional Philly new construction, is not easy to insulate and air seal properly according to Passive House standards. For this reason, we will probably never have these types of details that jut out or back from the facades in order to maximize efficiency and affordability.
    Thanks again for the great post and thoughtful comments.

  6. michael

    Paul Jacques Grillo wrote a great book about Archetypes. The title is Form, Function and Design. This is a must read for anyone in Architecture or Landscape Architecture.
    When I read the book the first time – a couple of decades ago – I had a “duh” moment as I think most will. The book is facinating for its common sense…about creating a strong kinship between human kind and the places we live. I’ve read it a few times since…keeps me on track.
    At some level the book asks why…why for example do we unwhittingly attempt to design or fashion spoons and forks into so mant different shapes. The idea that there is but one perfect spoon and fork for all of us with a thumb makes sense and relegates all else to glitter.
    …the houses may look modern but the cultural forces at work during the dawn of the modern era no longer exist. And I personally believe modern architecture propigated many philosophies and products that pushed us up against mother nature. But that’s another debate.
    As you wrote Adam, these houses look modern but it appears as though they are, with some irony, much better suited to sustainable living…long low over hangs would help keep summer sun out of the windows…the overhangs on my house cast shade a few inches below the bottom sill in late june here in the North East…it’s in Paul’s book.

  7. Adam Eran

    As a former resident of a passive solar home, I can testify that storing heat is no problem in the winter. Storing “cool” in the summer is also possible, depending on the climate. In Sacramento (where I lived in the home), the nights are cool, and we’d open the house during those cool nights. I remind you that Sacramento has 100+ degree summers.
    That said, there were about two weeks when this didn’t work. We spent a few bucks and got a wall air conditioner. That did the trick. Not perfect, but perfection was not worth living with the discomfort of an 80 degree house for about two weeks a year.

  8. Kevin

    Urban planners are key. The majority of street plans should have house orientations facing south. In N.American grid style plans this is not difficult.

  9. Kevin

    In terms of passive solar cooling. Use thermal mass which absorbs heat during the day and releases it at night. Trombe Walls too increase convection and open your upstairs windows.

  10. Greg Tolman

    A flat roof is often the best roof in snow country, because the snow that accumulates is excellent thermal insulation, and because there is little risk of snow sliding off, which often causes property damage and injury.
    Remember that a “flat” roof is not really flat, but is slightly sloped to drain melt and rain water. In snowy areas the drainage should be toward the heated center of the building, so that the melt water cannot refreeze on the way down, causing ice-damming, leaks and often dangerous icicles. In rainy areas, the drainage system needs to be engineered to handle the biggest downpours, with backup drainage for exceptional rains or clogged primary drains.
    Regarding aesthetic issues, perhaps a taste for “boxy” buildings is an acquired one, but I for one, grow weary of buildings that strive to appear older than they are, fashioned in some historical style, or more often in an uninformed mash-up of traditional looking details, including roofs bristling with hips, gables, dormers and faux chimneys. Not all modernist buildings are lacking in grace, harmony, even charm.

  11. Mark

    Yes, you are correct, unless the incoming air is first run through an underground vent. The earth is always about 55 degrees F at 6 feet underground (unless you live near the poles). If the vent shaft is at least 30-40 feet long, then the air will cool. The longer the underground intake shaft, the closer it will drop to 55 degrees. I think the only issues are with humidity. There is an entire mall in Zimbabwe cooled this way. It is called Eastgate. It uses NO air conditioning.

  12. Patrick

    We own a 100-year old home in Halifax, Nova Scotia. Our roof is flat, just like row homes in Philadelphia. We’ve got a maritime climate (North Atlantic) and it rains and snows a great deal. There’s a slight pitch on the roof to take the rain off. Snow is not considered a problem. Roofs do not collapse. In short, flat roofs with a slight pitch work just fine. There are tens of thousands of them in East-Coast cities on up into this neck of the woods. In short, there’s no added drama with a flat roof (slightly pitched).

  13. Angie K.

    My parents complex in Florida had truly flat roofs. They all leaked. When my parents replaced their roof they had a slope added and used better materials than had been used previously. It doesn’t leak. To me that is a sloped roof, not truly flat. So, yes, if you consider slightly sloped (I think their’s was a 3% grade) roof to be flat, then they do work.
    One of my favorite boxy styles is Prairie. It still has style, but is kind of boxy. I couldn’t live in a plain box with no balconies on upper level floors, some variance in lines, etc. Some of the prefab homes I’ve seen lately are boxy, but still manage to have some style. Good design doesn’t need to sacrifice style or efficiency. It finds ways to have both without resorting to the excesses of historical ornamentation. However, a box, like the one pictured in the article, just clashes with nature and hurts my eyes.
    Since most people have little design sense, the chances that buyers of plain boxes will actually alter (and I guarantee people will want to alter) these types of homes properly to add some charm and warmth while still honoring the original intent are rather slim. It would be helpful for the designers to offer basic and enhanced drawings to aid in later transformations so that the intended beauty isn’t altered to ugly. Let’s not trash all historical ornamentation either. Let’s instead think of ways to marry good sense, history, and efficiency. Human nature, being what it is, compels us to desire uniqueness. That requires balancing past well-established design with new design in a way that makes sense. In part, we must not eliminate all art (ornamentation, shape, color, etc.) or we will eliminate that which, in part, makes us human.

  14. Judy

    A roof like that would be ideal, if designed properly for load and moisture, to take advantage of a living roof. Residents could plant low maintenance, native, drought tolerant plants and trees there. That would provide a benefit to the residents of the house (they can go up and enjoy it) and also of the surrounding area of the city (in helping to lower temperatures in the “heat island”).

  15. John Daniels

    I would like to know more about the 100K house. Please forward.

  16. gene rajaratnam

    awesome idea,how can I do this in Palmdale ,CA?please call me @ 6618037067

  17. David Kuykendall

    The concept of the 100K house is a great way of showing how integrated sustainable design can be a realistic goal for future home owners. I look forward to seeing more of these in the future.
    -David Kuykendall

  18. John Daniels

    I want to build a 100k house. How do I get the plans and specifications?

  19. Chad Ludeman

    Good comments here. We are not building outside of Philly yet, but do have plans to expand in the future. You can keep up to date at our blog or sign up for our newsletter at our Postgreen site if you want more updates.

  20. John Daniels

    Why is it so hard to get a set of plans ans specifications on how to build a 100K house? Whould someone please guide me in the right direction. Thanks John Daniels

  21. Kevin

    I appreciate the modern aesthetic and simpler forms do reduce cost. However I always check our energy models to see what are the significant factors in reducing energy and the answer is always the passive factors , orientation, and form of the building ( including window placement and shading) sealing, insulation and defeating thermal bridging…. none of it exciting for the general public. Given that minimal shading of glazed openings goes a long way to reduce cooling loads and consequently reduces costs/energy input to achieve comfort I don’t know why overhangs and some minimal fixed shades could not be integrated the design. Shades could be positioned with with transom panels to bounce light deep into the interior and reduce artificial lighting requirements. I addition, the durability of the building is increased with protection of the cladding materials, window joints and sills from water washing over them. All those cornices and watertables of traditional buildings are not just decoration.

  22. Adam Stein

    Hi John,
    The developer of the 100K house is a small start-up still in the early phase of building out their business. They’re working on a lot of stuff at once — improving their house designs, acquiring land, construction, their web site, etc. One of their stated goals is to eventually make specifications available to outside developers, but these things take some time. For now, I’d recommend spending some time on their web site, which is a really rich source of information.
    – Adam