Thursday, May 6, 2010

Getting more Technical

This post will outline the energy and sustainability features for what seems to us to be good house design and Passive House Design: New ideas and information and changes to ideas will be added as time and knowledge allows - we'll elaborate on each point in future posts.

Principals of Sustainable, High-Performance Buildings as we see it:

Primary Issue: "It's the Energy, Stupid":
Research shows that the energy used by buildings over their lifetimes far outweighs any other factor related to the building's cost to the earth and environment such as embodied energy in the construction process, wastes generated, naturalness or recyclability of materials, etc. 'It's the energy, stupid' is a phrase by Joseph Lstiburek - seek him out to learn much more about building sciences - will provide a link and article on this later.

So, in short, here are the points:
  • Give Priority to Low-Tech High-tech: Do the unglamorous simple things first, such as proper shape, orientation, fenestration, thermal mass, superinsulation, tight construction, and get these fundamentals right before turning to active energy systems such as PV, geothermal, etc.
  • Use the PHPP software to analyze and optimize the house design. This is available from the Passive House Institute USA for $225 as of May 2010
  • Maximize solar gains in winter - Careful, high-performance fenestration, building orientation. R8 Triple glazed windows with low-profile, thermally broken frames, high quality seals, and non-conductive spacers. This also means you need a clear path to sun on the south side, few or no windows on the north side, and moderate windowing on east and west. Depth of window reveals should be small on south and East sides, deep on the west side to avoid summer overheating unless there are other shade features such as trees, screens, or another building.
  • Minimize solar gains in summer - fenestration, overhangs, shading and orientation. Overhangs are the main way to do this - they have the advantage of providing clear sight through the windows at all times (as opposed to sliding screens), no moving parts, and no maintenance. The disadvantage is they become part of the lot coverage - for single-storey window sizes (say 5ft tall), overhangs over south windows need to be in the range of 4ft for houses in the Toronto area. This means a sacrifice in building size, which can be a problem at times. The difference in winter to summer solar angle is 47degrees, but due to lag (the winter solstice occurs at the beginning of winter rather than in the middle) the overhangs and co-ordinated window sizes need to work with a smaller angular difference - say 30deg or so, to better block out the summer sun, and maximize gains in winter over the glass area. In Toronto, the solar angles from horizontal are 22.8deg on the winter solstice, 70deg on the summer solstice. There are many websites on line providing the values for any location on earth, including a Nasa website.
    And one more thing: Absolutely no skylights, unless you can prevent heat losses through them in winter and the massive heat gains through them in summer. Here is a link to a research project in California where they built a house with no AC
  • Maximize air tightness in order to allow control of energy and indoor air quality. This means very tight construction or alternative methods such as the PERSIST method, and eliminating penetrations through the thermal envelope - such as dryer exhausts, kitchen exhausts, garden hose taps, vent stacks, AC (should not be installed), etc.  The dryer is something we plan to eliminate - by providing space to hang-dry clothes instead. The HRV inlets and exhausts will be through the basement floor. The vapour retarder and air barrier will be placed on th eoutside of the inner wall.  The walls are a double-wall construction, of total 20" (51cm) thick, with the inside wall 2x6, then a space, then the outside walls also 2x6, so placing the vapour barrier on the outside of the inside walls will mean none of that finicky detailing so often messed up, with all manner of plumbing and wiring penetrating it. There are some issues with this approach -added cost, and how to fill it conveniently with insulation.  I am leaning towards cellulose insulation.  There are some excellent articles on air barriers at

  • Maximize the efficiency of the subsequently required ventilation system - HRV, earthtube
  • Maximize the effectiveness of the thermal envelope - super insulate: in the Toronto area, R60 walls, R40 to 50 basements, R80 to 120 Roof (in US imperial units) is approximately what is needed. Current minimum code requirements are R19 walls and R32 Roof, and I think R13 foundation for the top 4' of the wall only. The house in these pages is approx those higher values. Doors are especially bad energy losses- and very little in the way of high-performance doors is presently available - something like 5 or 6" thick doors provding at least R20 would help a lot. One can make the door oneself, of course - If anyone is doing this or has done this, please let me know.
  • Minimize thermal bridges in all framing, windows, doors, detailing, foundations, penetrations. This, and the airtightness of the building, means careful and high-quality detailed construction using a good crew and good management, adhering tightly to the thermal-bridge-free design details. Thermal bridges can be major sources of heat loss, especially for example an aluminum threshold on an exterior door, attached to a hydronically heated concrete floor. Aluminum is to be used carefully, as its thermal conductivity is about 10 times that of steel or stainless steel. Wrapping the building in a layer of ridgid foam insulation helps a great deal. New passive houses may be designed to go beyond that by using double-wall constructions, and carefully detailed assemblies at openings.
  • Minimize the surface-to-volume ratio of the building. This means bulky, cubic or spherical shapes work best. The pattern language website suggests buildings be made as 'wings of light'. Narrow, long arms stretching away from each other, so more interior spaces have access to exterior walls and therefore natural light. Two additional advantages of this approach are that the buildings can shape their outdoor spaces into various partially-enclosed spaces, and there are interior spaces in the building which are away from other spaces. The 'Wings of Light' concept has major disadvantages when it comes to energy demands. Not only is there a lot more exterior surface exposed to weather (accompanied by increased space conditioning demands), there are numerous additional detailing elements (roofs get more complex, for example), there is a major increase in floor areas lost to insulation, and the cost of construction increases (I would think significantly, due to exterior finishes and insulation).
  • Maximize interior daylight, and minimize artificial lighting- this is just good house design. It seems incredible to me that so many houses being built today really don't do this. Look at any development marketed to the average home buyer, and you'll find the houses are arranged with adjacent houses directly (just 4ft perhaps) to their south. Such a house could never bring in much light, nevermind introducing solar gains. The fenestration of the houses was intended for the house to face one way, but the site planning dictates the houses are placed in any orientation that maximizes the dollar investment and use of the land. This means there are thousands of houses being built right now that could never be converted to become a passive house unless the adjacent house is removed. The other point about natural lighting is that it is much more charming than artificial lighting, and consumes no electricity.
  • Minimize the lengths and number of plumbing drains and vent stacks, especially vent stacks - A vent stack can be avoided by using the air-admittance-valve (AAV), but many municipalities will not accept this as yet, I think.
  • Minimize the lengths and number of hot and cold supply piping runs
  • Allow windows to open so summer and shoulder season ventilation and comfort is maximized
  • Take Advantage of Colours and Finishes:
    The following wikipedia article is a pretty good intro to the reflectance and absorbtion issues of solar radiation.
  • Maximize internal thermal mass - concrete seems the obvious choice, but more info is needed on materials like gypcrete and water, both of which have high heat capacities, one of which has low thermal conductivity - modelling heat flows based on day and night fluctuations in insolation, heat capacities, and thermal conductivities seems quite complex to me, though I think there are rough guidelines out there on this.
  • Build for longevity, durability, permanence, fire, earthquake, flood and break & enter resistance
  • Build for long-term lovability, practicality, versatility, utility
  • Design for high occupancy rates, for life changes - upsizing, downsizing, barrier free, ease of reconfiguring
  • Design for bicycle, scooter, walking, strollers, not just car
  • Build for food security - farm, garden, greenhouse, food storage, drip irrigation, urban livestock
  • Build for efficient use of space - Thin high-performance walls are better than thick, in this regard - balance with utility - make use of attic and basement space
  • Build for toxin-free interiors - radon, pollution, off-gassing
  • Build for moisture control and water management

Desirable and Doable Features:
We would love to incorporate all of these, but perhaps not all at once:
  • Seasonal energy storage - BTES (see the Drake Landing Link)/geothermal
  • Rainwater collection
  • Grey water recycling
  • Minimize water use, maximize water collection
  • Minimize demand on city drains, electrical grid, gas supply, water supply
  • Solar thermal and solar photo voltaic
  • Hydronic in-floor heating-cooling

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