Want to help me build my house?

By | September 11, 2015

Why a zero-energy-house is not economical in terms of energy needs, and what would be more efficient and economical

My partner wants us to build a new house. I'm against a new building – that is, unless it costs less to heat and cool than an old building. Do you think you can help us figure out how to design such a house?

The problem with current low-energy houses
Europe, and Germany in particular, is quite hot on energy-saving construction techniques. But I'm a hands-on homeowner and I'm no fan of these new passive house designs – in my experience, insulating actually drives up the energy costs. Want to know why?

1) The demand for fresh air. Zero-energy houses are designed to be air-tight. And we people have a strong desire for fresh air – so strong, that we open the windows every day to trade the stale air indoors for fresh air from outside. And we're not as "bad" as other families, which leave the window constantly open in winter! Result: the actual effectiveness of good insulation is severely reduced by our leaving-the-window-open strategy of getting fresh air.

2) The prolonged heating season. Thanks to the good insulation, the house stays cool longer than it had before the insulation. That means, I now have to heat the house into June.

To be very honest: I have not noticed any savings in terms of the amount of fuel that I need per year.

A more economical approach to the passive house problem
Did you ever wonder how the traditional Eskimos managed to keep their igloos above freezing, despite the walls of ice, the frigid temperatures outside, and an open door and ventilation hole? Or did you ever wonder how the ancient Persians managed to keep their lofty desert mansions cool, despite the scorching heat and freely circulating airflow? If we took that as a starting point… then the energy requirements for a modern house could be lower than what we have today, especially for an average family who wants a lot of fresh air.

Yes… environmentally friendly systems for heat exchange and heat retention! So, let me start with two questions:
(1) Are you aware of any other traditional temperature control mechanisms, such as the sunken igloo entrance and wind towers alluded to above?
(2) How could we adapt those solutions to outfit a modern passive house, and yet keep the open air circulation concept instead of focusing solely on insulation?

40 thoughts on “Want to help me build my house?

  1. Garron Longfield

    +Sophie Wrobel This will be my last post on this string. I believe it is important to mention some essentials if one is to try a hands on design of a green home. There are usually two things we desire in new homes: The best home for the least amount of money and we want it right away, especially the (payback)
    Therefore, there are some things that one should consider.

    There are pros and cons to every material and/or technology in building design. Many people will promote the pros. Therefore it is essential to know both to make an informative decision. Also to try and compensate with design later. Which brings me to my next point.

    In designs there is always a diverse mix and gray area of exterior and interior with more emphasize being placed on interior and exterior aesthetics (design system). However, stay focused and take it in parts. As a result, the exterior or the envelope wrap which includes the exterior walls and foundation, materials and design are primary. Afterall, we want structural integrity with aesthetics and the U-values will decide further development with the interior.
    Now some terms you may hear that might confuse.

    Air tightness is not the same as breathability. Also air barriers are different than vapor barriers. I discovered a good guide from ECOhome (somewhat biased) that gives a good overall basic view of some of the concerns. My link deals with air and vapor barriers but on the far right is an index of the green guide. They also offer videos for the do-it-yourself person. http://www.ecohome.net/guide/difference-between-air-barriers-vapour-barriers
    Hope this may help some. 🙂

  2. Sophie Wrobel

    +Garron Longfield Thank you for the deep insight – and I agree completely. Your example of window placement has already been demonstrated to make a difference – if you look into the team behind the link that +Frank Nestel posted earlier, they claim that the calculated efficiency of the polar-bear-pavillion is only possible because of the placement and size of the windows (south-facing in the northern hemisphere). If they were placed on the other side, the concept wouldn't work.

    That said, it will be some time, and some trial-and-error of mixing up various concepts to see what comes out, in order to find the sweet spot between regulations, energy efficiency, and human habits!

  3. Frank Nestel

    *Remark: * It all very much seems to depend on where you come from. Climate makes a difference (even between northern and southern Germany BTW), habits make a huge difference, i.e. many Germans are not used to cooling their houses (cars are a different story) and requirements vary a lot some people prefer 20°C as a basic temperature, some want much more and similar things apply to fresh air.

    Apart from that, there is a tendency in Germany in certain "circles" to have zero energy or even negative (i.e. home produces more energy than it consumes) energy homes and what is counted is usually not only heating, but also electrical power consumption. Me for my case I live in a very conventional house and why we really made huge steps forward conserving energy, our house will never become zero energy though we already spend more then probably reasonable from a pure financial point of view.

  4. Garron Longfield

    +Sophie Wrobel First do not underestimate the value of insulation. Extremes such as more or none is not necessarily the best alternatives As with most things there is a give and take. There are different technologies and answers. However, there is not a one size fits all answer.

    You are doing the right thing to consider alternatives. There is a concept that is gaining popularity to new construction: The whole house system approach. The approach considers a house as an energy system with independent parts each working together that effect the whole.

    For example; super insulation, air tightness (passive house) have stringent requirements but is it cost effective? An ex of an alternative: http://thesustainablehome.net/?p=413

    Let's look at a example of a whole house approach. https://www.cedengineering.com/userfiles/Heat%20Loss%20Calculations%20and%20Principles.pdf
    This example shows the engineering used to evaluate but not necessarily the conclusion on final elements. For example; it shows that a double glazed window is more efficient,but it does not take into consideration the different designs and placement configurations. http://energy.gov/energysaver/articles/energy-efficient-windows.
    One may suggest a design that is more efficient. However, does the increased cost and added efficiency really make that much of a change?

    Therefore, taking the different parts and incorporating them into an efficient functional whole can be cost effective and energy efficient. Sometimes little things can make a difference such as ceiling fans.

    Of course there are other variables to consider such as moisture control, thermal flow, climate zones, etc.etc. Then add building codes and minimums required for energy credits.

  5. Sophie Wrobel

    +Garron Longfield Yes, I live in Germany. I can assure you that the payback for retrofitting is very, very slow… I expect my initial investment to never pay off. My heating bill for a 100-year-old building before retrofitting clocked in at 17400 kWh in wood and oil per year, or an average of 'only' 80€ / month. A comparable new building costs at least 100€ / month in heating when it is efficient – despite a lower energy requirement, it costs more, because (1) electricity is involved, (2) it involves centralized heating instead of decentralized heating, and (3) the good insulation cuts off the effect that the natural heat sink and natural shade from the giant tree in the backyard that my old house had isn't taken advantage of in summer anymore.

    Anyway, after retrofitting the roof, our energy consumption rose by around 5000 kWh per year, primarily due to needing to heat through the summer despite the energy savings during the winter as a result of the insulation.

    Before retrofitting: 10 degree temperature difference in summer (= comfortable temperature)
    After retrofitting: Don't have exact numbers because the heating was on, but I'd guess at around a 16 degree temperature difference in summer.
    Energy savings during winter: around 2000 kWh
    Energy savings during summer: around -7000 kWh

    That experience has rather soured my opinion on 'good insulation saves energy' – if a natural heat sink with good insulation is too efficient for the climate here, then there's got to be a better way to harness the energy more efficiently in a new building to take advantage of that 16 degree temperature difference than by increasing heating costs to counteract the overefficiency. With a chance to build a new house, I'd really like to capture that advantage, and improve on just the heat sink if possible!

  6. Sophie Wrobel

    +Frank Nestel That looks quite interesting – reversible chemical energy storage would be useful not just for storing warmth, and a textile surface sounds like something breathable. I wonder what the specifications for those constructs are.

  7. Per Siden

    +Sophie Wrobel there is no requirement for cooling, I can assure you that.

    In Sweden it's otherwise very common with district heating (and in some areas cooling). Combined heat and powerplants (CHP) are very efficient compared to plants that only produce heat or electricity. Mostly these CHP plants use household waste as fuel, some use forestry waste.

    Distributed heating and cooling is also very common in neighboring Denmark. Almost every municipality have it. It's cheap and it's efficient.

  8. Per Siden

    +Shaker Cherukuri​ Maybe not exactly a mansion, haha, but pretty much that size yes.

    Average temperature (over 24 hours) in July is +14°C. In January it's -13°C. Peak temperatures range from -35°C to +30°C, unless it gets really extreme.

  9. george aiken

    Why not develop or find a way to have insulation that you can take out during the summer, and put back in during the winter? A lot of the problem you mention seems to deal with insulation.

    The other part you mentioned was fresh air. In the summer, hanging a wet cloth in front of the window will help since evaporation takes heat out of the air. For the winter, I have read that it is very house specific, but one thing that would be neat would be a roof that can change colors, so it can be black in the winter to absorb heat, and white is the summer (assuming you aren't already using solar or don't have other plans for your roof).

  10. Garron Longfield

    +Sophie Wrobel Aw I take it you live in Germany. I have done some research on Germany. The main reason is their recent push on architecturally designed passive homes (passivhaus) which is somewhat lacking in America.

    One thing I discovered is they put much emphasize on energy efficiency, particularly HVAC which includes ventilation, heating and AC.

    As a result there are some things to consider. To retrofit an existing building the highest level of performance may not be possible and the cost may be higher thus savings (return) on initial investment may be slower. On the other hand, efficiency can be cheaper to build into new construction with a higher return rate. Another consideration is that new designs can be designed with less sq. footage which has a positive effect on efficiency. Just some food for thought.

  11. Sophie Wrobel

    +Shaker Cherukuri let's not forget, that the Scandinavian climate that +Per Siden lives in probably requires less cooling in summer and a lot more heat in winter than a southern US climate!

    +John Poteet and +Per Siden The cost of electricity has risen over 10% per year for the last few years here. Oil has dropped considerably to the price it was seven years ago, and wood has increased only marginally. So to make economical sense to change over to an electrical-based heating system (geothermal included), the system would need to be more than four times as efficient as an unecological alternative to make economical sense. The electrical fan outside is a major problem too – it is too noisy for a residential area, and would need a special permit to operate (not impossible, but at the same time it's not the nicest background noise!).

  12. Shaker Cherukuri

    +Per Siden My peak is 2000 kWh per month for 4 summer months and same equivalent for natural gas in the winter 4 months. 1000 kwh that rest 4. 20,000 kwh/year. Yours sounds like a 10,000 sqft mansion😀

  13. Per Siden

    +Shaker Cherukuri​ hardly any at all. Heating is entirely disabled once outdoor temperature is +16°C or more, and the day surplus means it won't run at night either. Besides, the sun is only set for two hours so during the summer heating is not really an issue at night either. The only consumption is for a modest production of tap water.

    Now, winter is something completely different. Year average consumption is around 40,000 kWh. That's low compared to the previous 12-15 m3 of oil, part of it due to added heat exchangers for more efficient ventilation, and better regulation and control.

    But it's hardly a zero energy house.

  14. John Poteet

    Geothermal heat pumps run cheaper than gas fired heating and standard AC in most of the U.S.. If you can put solar panels on a roof to cover AC costs like we do in California you can run a geothermal heat pump anywhere but Alaska.

    It turns out that the fan on the external heat exchanger is much more costly to operate than pumping high pressure gas through ground loops.

    If you combined optimal systems such as straw bale walls, triple paned windows and r-40 ceilings with a geothermal heat pump you'd have a very low energy cost for HVAC well within a modest solar pv system.

    There are also systems which combine solar thermal panels with ground loops in Canada, and Germany for added winter heat. The trick is that the heat from the solar system is added to the ground loop keeping the "thermal bottle" underground warm.

    The problem with passive systems is that they involve huge piles of rock/soil behind, under, around the house to maintain the heat balance and then you have huge windows you have to find a way to shade in the summer.

    edit: Here's a combination of geothermal heat and passive solar

    The page I found it on:

  15. Per Siden

    +Sophie Wrobel​​​ I would classify geothermal together with heating your house directly from electricity, except you get roughly twice the amount of heat per kWh.

    I have installed a 35 kW geothermal pump myself. It requires at the peak of it's duty cycle 20 kW of electricity, but on average much less. The heat pump and its 3x400m of hose at 1,2m depth replaced an oil burner that consumed on average 12m3 of oil a year. It supplies both heating and hot tap water.

    It's a really big house in a cold region. For a smaller building in central Europe much less is if course required. You wouldn't want to invest in overcapacity that us never used, there is a sweet spot at being able to provide your heating in full for say 90% of the year.

  16. Sophie Wrobel

    +Garron Longfield​​​​​ building materials is a very good point. And great links, by the way! This is one of the things which old houses feature (at least, i have such a house, though the wall insulation isn't the best) but the thermal mass for straw-and-lime constructions typical of the houses at the turn of the last century alone are not sufficient to get the house approved for building today. Thick blocks of certain concrete today are available, but to achieve the required temperature conductivity value (apologies if this term is slightly incorrect, as I only know it in German. It's symbol is lambda?) it would require such a thick wall that the sunlight through the windows would be too low for natural comfort… Or the rooms so large that I can't clean them easily. Looks like something to combine and see how efficient the final design turns out to be.

    On that note, another idea that comes to mind: Ivy and green roofs also provide a thermal insulation layer end to trapped air pockets they create and light absorption during hot summer days. This is, however, not recognized by the building code in terms of calculating the energy requirements to approve the construction permit.

  17. Chris Collins-Wooley

    The link I provided above deals specifically with the problem of replacing stale air in an airtight home without wasting the energy it took to heat or cool it. I built one out of curiosity. I took sheets of corrugated cardboard and alternated the corrugations 90 degrees with each sheet, built a cube. I used fans to push air through the corrugations. It was surprisingly effective and had the added bonus of preventing pollen and dust from the opened windows.

    So I installed my experiment in the ducting of one of my home's forced air exchange systems by adding a duct to the outside. But — and here's the rub — even though the air was fresh, certain members of the household still insisted on opening windows. It was a psychological thing. I eventually removed it.

  18. T. Pascal

    I forgot that you were interested in passive systems. The idea is the same, but you would build the house in such a way to encourage air-flow (tall ceilings, lowered entrances, narrow or wide houses aligned with prevailing winds, etc.) These options are not as suited for urban or dense living probably.

  19. T. Pascal

    This discussion came up in a slightly different way recently: a friend of mine had a special exhaust fan that blows air from inside the house to outside. He turns it on at night when the air in the house is too hot. I have never heard of any actual examples like this because it seems very rare. Most people (like you and I) open the windows a lot.

    You are absolutely right that most designs are closed and air-tight. Maybe we just need to include an inside/outside switch to units so that, say, if it is cold inside, then pull warm air from outside and if it is warm inside, pull cool air from outside. During normal operations or fan-only modes, it could mix the air. Or do exclusively exhaust with negative pressure. Or positive pressure.

    Something like this seems very feasible and just needs some spark of ideas and designs to prove the concept.

  20. Garron Longfield

    +Sophie Wrobel Agreed but, one geothermal alternative is the energy from the ground which does not necessarily need a huge tract of land. However, it must be installed properly to achieve full benefits. Therefore, one must research to find a competent professional contractor.

  21. Garron Longfield

    +Sophie Wrobel There is another thing to consider if building a new home. The building materials.For example; you mentioned ancient techniques. One is that in dry climates mud bricks or adobe was used. This was effective because of the thermal mass. In deserts, temps fluctuate during day and night. It retarded heat transfer during the day ( a type of heat sink) and with its capacitance to store energy provided a barrier to temp drops at night somewhat like a thermal battery.

    Some possible alternatives; concrete, bricks etc. Some say wood is good but in reality it is not as efficient. Of course this depends on climates. http://www.yourhome.gov.au/passive-design/thermal-mass

    Another possibility is the use of straw bale wall construction that was used in the past, in Europe and the U.S. and is gaining renewed popularity. i.e. http://www.oberlin.edu/news-info/98sep/strawbale_history.html
    Again dependent on climate which as everything has pros and cons. http://thelaststraw.org/who-are-we/history/ Which brings up the issue of homeowners insurance acceptance.

  22. Sophie Wrobel

    +Garron Longfield​ oh, zero energy is more of a marketing term here than anything else. I think geothermal energy has a lot of potential (and +Per Siden​ would agree too, I'm sure). But it is quite extensive and wouldn't be suitable for a limited land solution.

  23. Sophie Wrobel

    The problem with heat pumps is the high cost of electricity these days. They are reasonably priced for a new house when installed right from the start, but not very cheap to operate. That makes heat pumps an efficient but expensive source of temperature control. And then there is the 'if installed properly' catch. But perhaps a heat pump coupled with a cold sink in winter, or a wind tower in summer?

  24. Garron Longfield

    +John Bump I noticed you mentioned heat pumps. There are many different kinds each with positive and negative concerns. Some of these are efficiency, cost, durability and climate and site conditions to name a few.

    I believe, you then went on to what is called geothermal and I agree, should be considered. Geothermal heat pumps can be quite expensive but are efficient (low cost operating) and reliable "if installed properly".

    For example: Depending on the climatic environment a geothermal heat pump system installed improperly can loose efficiency in lower temperatures. Theoretically this should not happen because at the right depth the earth maintains a somewhat constant temp.

    Did you know that there are now earth tubes that are not the same as geothermal heat pumps but instead provide a passive heating and cooling alternative along with providing fresh air circulation.

  25. John Bump

    Have you looked at heat pumps? Using the thermal mass and thermal inertia of the earth allows heating/cooling efficiencies that are arguably above 100%, as you're extracting the thermal conditions you want from somewhere else. I'm a huge fan of insulation because I can choose whether to use it or not, by what I do with the windows. Not having the choice kind of sucks.

  26. Garron Longfield

    +Sophie Wrobel This is a deep, multiple question but I will try to answer with some basic physics and engineering.

    First trying to achieve a zero energy home with current technology is not realistic. The options would efficient or ultra efficient.
    +Chris Collins-Wooley gave a great link that you should consider. In fact, many high end homes are incorporating this technology in their new homes.There are many ways you can go some good, some bad, depending on climate and other variables.

    Which brings me to the point that you should first do an assessment of local climate and site conditions, including local requirements and codes for some of the technology such as energy grids or wind turbines etc.

    You mentioned older designs such as igloos and Persian homes. Some of these are actually being used but again it depends on conditions. For example; ancient technology for cooling. In dry hot climates a few things were used. Deep set small windows, lattice, cross ventilation and water evaporation. Many places in dry climates such as Sacramento CA. use what is referred to as swamp cooler or cooling towers. They are more energy efficient than air conditioning but would not work well in very humid environments. However, water air conditioner technology has improved which can remove some of the humidity from incoming air but is not as efficient.

    Igloos utilize snow as insulation and a dome shape to reduce wind resistance, plus it relieves building stresses. Also the sunken igloo entrance has an advantage. Actually the make more permanent igloos using three tiers. The concept relies on basic physics. Cold air sinks and warm air rises. Therefore, the door usually covered with hides acts as a cold sink. the fire or heat is produced on the middle tier while the heat rises and the ventilation for smoke removal occurs at the hole. Since snow is such a great insulator the heat and a few people can maintain a temp. as high as a 70 degree difference.

    Since this is a comment I hit some of the basics but I hope this helps. 🙂

  27. Frank Nestel

    Shouldn't the air circulation of a zero energy provide enough fresh air and opening a window is merely a ancient habit? ((I still wait for a "Tatort", where a burgler first gets the inhabitants of such a house at sleep by putting some narcotics in the intake)). In general, since climage, taxes and other things are unpredictable, I'd rather stick on many methods at once, i.e. usage of solar energy both for electricity and heating, good insolation, air heating system. If you do so, I still wonder, if you can have so much surplus energy, that you can even consider to push some cooled air in the house, without feeling guilty ..

  28. Sophie Wrobel

    +M Sinclair Stevens Look forward to discovering what book you're referring to!

    There is one other heat storage system that I've run into, in addition to the ones in the post: the traditional 'ice house' (basically an underground heat sink coupled with a heat exchange pump – it works in both directions). I do have blueprints for all three; hoping to discover more ideas and put them together to create a house.

    My partner is betting that by combining traditional design with modern materials, there's a way to build a porous, yet energy-efficient house and get it pushed through the building regulatory board.

  29. M Sinclair Stevens

    Interesting questions to me as I'm in the beginning stages of planning a new house also. I talked with a man yesterday who was very proud of his air-tight houses and my reaction was the same: I like a well-ventilated house.

    I was reading a very interesting book on that. Leaving this note as a bookmark so that I can go find it for you when the household wakes up.


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