Monday, January 31, 2011

Updated Design

Here is our latest.  The building is rectangular, with a stepped gable roof.  The long south facade presents an improved oppurtunity for solar gains, but the north face is also longer, where more losses occurr.  Of course, a large part of the gable roof is available for solar collectors.  Outside dimensions at walls are 43' x 31'.  All walls are 24" thick, and insulation values are about R70 walls, R100 Roof.  All cellulose, with likely some mineral wool in the basement.  No rigid foams or virtually none.
The view is of the South and West facades.
To give the south facade untrammelled solar exposure, we've moved the main entrance to the West side.  the challenge we now have is to make the entrance obvious and inviting.  It is almost like having one of those snout-nosed garage designs, where the visitor must travel around the garage to reach the front entrance.  In this design also, he is to travel around to the side of the house to enter, all the while remembering the importance of solar energy!  We are playing with those West roofs, and may even make them somewhat enclosed.  The building has a small enough footprint, we have room to spare in the lot coverage allowance.  The East side faces the street, where there is a balcony attached to the 2nd floor master bedroom in that tower-like stone-covered end.  Below that is an adaptable space where an elderly couple can stay on the main floor - they have an entrance to the garden under the balcony.

View from the South West.

Sunday, January 30, 2011

Aerogel Insulations

Found a place where you can buy aerogel.  The product is a pelletized aerogel, rated R-8/inch.  Cost is $160/5 gallons - super expensive.  They also make translucent skylights using this 'nanogel'- visible transmittance 20%, R-20 insulation.

Saturday, January 29, 2011

Geo-Solar Seasonal Heat Storage

Solar Thermal is great - but if you size the system so there is no excess heat in summer, the available heat in winter is pretty low.  So the thing we all want to do is store excess heat from the summer to use in winter, and store the excess cold from winter to use in summer.

Our yearly energy demand of the house is 3600kWh for space heating, and 4400kWh for DHW, total 8000kWh.

To store 8000kWh of energy as heat, here is one option:
  • Not accounting for losses from time of heat input to time of heat usage,
  • Store hot water in a Tank - say we can use water from 0 deg to 80deg C (delta T is 80K)
  • Specific heat of water is 1.17Wh/kgK (=4.18kJ/kgK, as 1watt is just 1J/second).
  • Volume of water (M) needed:  M = E/(C*delta T) = 8,000,000Wh/1.17*80 = 85,470litres
  • thats a lot of water - a tank about 3m x 9.5m x 3m tall
We can improve this dramatically if we utilize the phase change of water from solid to liquid, since the latent heat of melting of ice is 92.8Wh/kg  (=334kJ/kg).  If we utilize the water from say a couple of degrees below zero to about 80 degC, the volume of ice/water required reduces to about 1/2 of what was before (about 43,000litres, down from 85,500)  but there is then the technical problem of dealing with the expansion and contraction of the ice - which I don't know how to tackle as yet.  You can imagine that a container about 3m x 5m x 3m tall can certainly fit somewhere on our city lot.

We can reduce the storage requirement further.  We don't need the capacity to store the entire year's energy demand.  Lets say we use the solar thermal system to it's max - then we just need to figure out what fraction of the energy needs are not met in winter, and store enough to cover that much. - surely much less than the 8000kWh.  Later, we'll also have to deal with the storage losses and system inefficiencies - so the amount of storage needed will probably end up near the 8000kWh anyway...!

Geo-Solar Seasonal Heat Storage and Other Information

I think this guy has the right idea. about Geo-Solar Energy systems:

Depth to Ground Water/Elevation of Water Tables in Toronto area:
This information is so far hard to find, but the below links might be a start...
I need this info to consider the thermal conductivity of the earth below and around the house.  This also has important implications for thermal energy storage in the ground.  A High Water table will mean foundation structural design will be affected and heat lost form the basement may be high due to the flow and thermal characteristics of groundwater.

Friday, January 28, 2011

Cost of solar Thermal

As of Jan 2011:

  • Flat Plate Collectors:  US$20/SF or $215/SM
  • Evacuated Tube Collectors:  Prices are ranging from as low as $127 to $300 to $340/SM

Heating System Design

Getting around to designing the heating system:

I would love to use radiant ceiling panels - these can both heat and cool the house, and take no floor space, and do not need the concrete floor for radiant heating.  Zehnder's carboline products are expanded graphite panels with copper pipes running through.  They can both heat and cool a house.  I wouldn't need very many.  The peak heat load is about 14W/square meter, and the peak cooling load in summer is about 10W/square meter.  Delivering heat via ceiling panels is not efficient, but with heat loads so low, and the almost non-existant stack effect in a passive house, I think this might be a practical solution.  In addition, it would be very easy to supplement the heat input by heating the ventilation air a little bit.
Next comes a bunch of number crunching based on:
Yearly space heat demand:  about 3600kWh (240 sq m floor area, times 15kWh/sqm-annum)
Yearly DHW heat demand:  about 4400kWh (based on 6 person occupancy at 25litres hot water at 60degC per person per day.  Apparently this is low for NA, where the daily hot water use is more like 60litres, but typical for Europe.)

Why Install a Low-Loss Header:

The following text is from:

Why should I fit a Low Loss Header? 1. Your boiler, particularly the heat exchanger in you boiler, will only function at it's peak efficiency when the water velocity passing through it is maintained within prescribed parameters. Boiler manufactures should tell you what the specs are for each make and model. In some cases the flow rate through the system circuit will exceed the maximum flow rate through the boiler, or it may be that the system flow rates are simply unknown. In other cases the reverse is true, where the boiler flow rate exceeds the maximum system flow rate (particularly true in some multi boiler systems). Fitting a Low Loss Header allows the creation of a primary circuit, within which water velocity can be maintained at the required constant, regardless of changes or requirements in the secondary circuits. 2. Not only is the water velocity important, but also water temperature. There are two potential problems: the first is "thermal shock". If the temp difference between the flow and return is to great, it puts a huge strain; through thermal expansion and contraction, on the heat exchanger. Also the temperature of the water passing through the heat exchanger is important, particularly with condensing boilers, these have there own specific requirements to operate at maximum efficiency. For a boiler to go into "condensing mode" the return temperature should not be higher than about 55'C. So in some cases temperature sensors are fitted on the header to allow control over the primary circuit temperature. 3. Because of the reduced water velocity, the header is an ideal place for siting an automatic air vent for removing air and a drain point for removing sediment and debris. These are generally fitted as standard on most headers 4. The header allows separation of primary and secondary circuits for easier diagnosis when problems occur.

Aluminum Foundation, Steel Foundation for Residential Construction

So lets start figuring out these metal foundations for basements applications:

This is actually a wood foundation clad with a thick layer of galvanized steel.  There would be a poured concrete base.  Then the actual foundaiton would be a wood stud structure, double-shelled, filled with insulation.  Then towards the outside, there would be an air space of about 1.5 inches created with something like Unistrut, though I prefer something cheaper (unistrut is so expensive).
then the galv steel cladding.  We're talking about 11 gauge (0.120 inches thick), welded or screwed (that would be annoying) to the unistrut from the outside.  Stich welded between panels.  Zinc oxide gases coming off everywhere fromo the welding, - gas masks for the welders -
I got a price on the galv steel sheet from North York Iron - $107.25/sheet (thats $.67/lb), 37 sheets (148ft perimeter on my building).  This is for a total cost for the sheets of $3968.  The sheets are heavy, 160lbs each, so not fun to handle - maybe some kind of small crane....But this way, one could make a very thin, and durable exterior shell for a building without suffering the 8 or 10 inches of concrete, probably for a competitive price.  The total shell thickness including the airspace can be about 2" or less.  On ecan get another 6" of insulation in the same space as for a concrete foundation.  The steel can be sprayed and a dimpled poly membrane installed just like a concrete foundation - for better corrosion resistance, though I've found galvanzied steel (doesn't have to be hot-dipped) holds up well.  No poisonous pressure-treated lumber involved, and carbon footprint could be similar or better than the poured concrete.  Thermal expansion co-efficient of the steel is similar to concrete, so not an issue.

Now:  Aluminum foundation:  Same idea as the steel, but no corrosion issue, unless you have a very salty and wet soil....Using the same 1/8" thick sheets, the weight of each sheet will only be about 53lb.  Lighter than a sheet of fiber-cement or drywall - much thinner, of course.  I would not weld these in place, I would use aluminum brazing, although corrosion-resistance of the braze would need to be checked.  This way, the foundation would be sealed entirely, and fastened well at the same time.  I would skip the dimpled membrane and spray.  Apparently the price of Aluminum is about $.65/lb - at this price we are looking about $35/sheet of 4'x8' - cheaper than 3/4" S1S fir plywood!
At first I thought thermal expansion would be an issue, but note that the ground temperatures are pretty stable - fluctuating only some 10 degrees C or so throughout the year.  But thermal conductivity of Al being so high, one might start to wonder if the ground around the foundation would get quite cold, even at the bottom - Hello Therm simulation.

Thursday, January 27, 2011

Fiber Cement in Below Grade Applications

I'm looking (without success) for a thin, impermeable sheet-like product for use in a below-grade exterior application.  What I want is a material like fiber cement, which is very thin, fire-resistant is good, and hard, and hopefully impermeable.  I'd like to apply it below grade like a very thin impermeable sheathing on a wood-framed below grade curtain wall.  I don't want pressure treated plywood due to its environmental issues.  Fiber cement seems perfect, but I just spoke with a Tech rep at James Hardie and he completely seems against the idea.  The product is made, he says, of type 2 cement, silicon, and wood fibre, and absorbs water.  But so?  Concrete absorbs water too - and we just damp-proof it with an asphaltic spray and apply that dimpled HDPE membrane below grade. - Or not.  Why not do the same with Fiber-cement?  I can resort to sheet aluminum, perhaps 1/8" thick.  This is certainly impermeable - but coefficient of thermal expansion is high - still maybe OK.
Next option - Fibreglass sheet - like those circuit board materials, only thicker.  Concrete sheet is thin, of course, that is an option, but costly as well.  Plastic Sheet - PVC is eww.  But perhaps HDPE, or PEX sheet?

Tuesday, January 18, 2011

No Stack Effect in Passive Houses

During our Passive House Consultants Training in Summer 2010, we were told empirical evidence is revealing is there is no stack effect in Passive Houses.  I'm referring to the way heat rises.  In normal buildings, the upper floors are warmer than the lower floors of buildings.  And tall rooms can be expensive to keep warm in winter because all the heat rises to the ceiling, while the occupants remain on the floor.

I found this claim of no stack effect fascinating but didn't know why it might be so.  After some thinking, I feel the answer is in the surface temperatures.   For stack effect to occur, there must be differences in air temperatures in a building.  In passive houses, all the interior surface temperatures are within 3 degrees C, throughout the year.  From our trainings, I understand this is even on the coldest day in winter, and on the hottest day in summer.  This means the stratification of air in the house is minimal, and that there is very little drive for stack effect to occur.  I would think in fact it does occur, but to a small degree only.

If you imagine a room full of air and the air is of varying temperatures, you expect that the warmer air will migrate slowly upwards while the cooler air stays lower, but what about all the air in-between?  If regardless of the room's height, all the air is within 3 degrees, one would expect a linear progression from one temperature extreme to the in a room 10ft high, the floor-air might be 18deg, while the ceiling-air is 21deg. At 5ft, the air might be 19.5deg.  All of this would be with no motion of the air at all.  Now if the heat source were near the floor and blowing a slight amount, there will be minute currents of air moving throughout the room.  You can see how this is getting pretty un-important, with these low temperature differences.  On the other hand, with a 10-degree C differential or more like in a regular building, the stack effect (and drafts of cool or warm air) might reasonably become much more noticeable.


Wednesday, January 5, 2011

The New Economy House

Marianne Cusato has designed an interesting house, not very big, but with 4 bedrooms, that can be built very cheaply, and provides some flexibility in living - perhaps even a rental income.  I found this approach very to our liking and thought, why not redraw this house as a passive house?
You can see the New Economy House here:

Things I noticed about the New Economy House:

  1. Not too much provision for a hall closet - if you wanted to have a basement, with stairs underneath the existing staircase.
  2. Bathroom layouts upstairs are a little tight.
  3. 2' thick walls leave the windowed facades quite a bit different looking from the original
  4. the 30" thick roof similarly has a strange appearance that needs to be addressed.
Here is a visual: