Friday, June 18, 2010

First Session of Passive House Training Completed Today

The first Passive House Training session in Canada started this past Wed June 16th 2010 and finished today.  It was quite a detailed look into the Passive House Planning Package software.  24 or 25 Students attended the training and the class was full of very interesting and intelligent building professionals.
Will need to consider a number of changes to the house design now!  Thermal mass is not as important.  In-floor radiant heating is not as comforting since so little heat is transferred into the floor - there is no warm-floor effect...

Monday, June 7, 2010

Grease and Smoke Removal in Kitchens

Here is quite a good intro article on grease and smoke removal, grease-fires and performance of range hoods and emerging research and technologies.

As I read more, it seems the right way to go is to use a grease and smoke separation unit as a range hood (available for commercial kitchens - not yet found one for residential applications...), which does not exhaust air out of the building, saving what seems to be a lot of heat, eliminating the need for make-up air and the cost of all that ducting, control, shuttering, etc.  There are now multiple strategies for removing grease and smoke from the stove plume - including filtering, centrifugal force, electrostatic precipitation (ionization), UV application, and some water spray technique.  Apparently range hoods sometimes employ multiple strategies.  Note dampers are not allowed in range hood exhaust systems, which means there would be a big hole in the house at all times if an exhausting range hood were installed- not at all acceptable.
In summer, all that waste heat from the stove stays inside the kitchen if the range hood does not exhaust the air to the outdoors.  This is probably somewhat addressed by opening a window, if there is no AC system.


Kitchen Range Hood 2

Having said all I did on the Kitchen Range hood, there is another approach, which is probably better.
Here is the link:
This is a company specializing in energy and ventilation systems for Passive Houses.  Basically, they are saying that a kitchen needs no special exhausting - the ventilation system will suffice.  It does, however, need a range hood for the purpose of removing the fat from the stovetop fumes.  they are not more explicit than that, but I think it means a range hood with grease separators, which just sends the cleaned, degreased and desmogged air back into the kitchen for the ventilation system to perform the final cleanout.  What a simple (and attractive) approach!  Will work to find out more about this.

Earth Tube

EarthTube - A pipe in the ground exchanging heat with the soil, forming the intake for the HRV system.  The soil temperatures (about 15deg C year-round) preheat the incoming winter air, improving the HRV performance quite a bit.  It also cools the incoming summer air.  In the summer, one would bypass the heat exchange in  the HRV unit and simply bring cooled summer air from the earthtube directly into the house.

Needs to be about 8" (200mm) diameter pipe buried 6-8ft (2m) in the ground, about 150ft (45m) long, sloped toward the HRV.  At the end of the slope, there will be a little well where condensate can collect and be removed.  A pipe with anti-bacterial coating on the inside would be good.  PH-Luft is a free online software which calculates the efficiency of the soil-to-air heat exchange, based on soil type, air flow rates, incoming air temperatures, and tube length and size, and so on.  The Passive House certificate accepts the results of this software in the certification process.  PH Luft is in German - bit of an issue to me, but struggling along a little bit with it.

Was told to avoid PVC for the earth tube.  Of course, it has the dubious reputation of being very environmentally unfriendly both in manufacture and in use - though there are two main types of PVC, one of which has little or no plasticizer - a major factor in eco-conscious debates.  The one with plasiticizer is the bad one, I think.  Trouble with this is that PVC pipe is commonly available, cheap, and easy to work, creating strong, tight joins with solvent alone.  Mechanically, I find it to have excellent characteristics for both the earth-tube and interior air distribution.  Alas, chemically, there could be issues, though I must say, I would like to find out more about this.

The recommended material is HDPE.  This stuff has to be joined by fusion-welding using a purpose-designed welding machine - I think one can see this process in Youtube videos, and its not available at the hardware store.  I found Oxford Plastics makes a variety of this type of pipe, and Corix are the distributor/installer/welder, in our area.  90deg Bends and Tees, and caps area available in the larger sizes, 8" diameter, and larger still.  Pipes come in straight lengths up to say 55ft (as long as a truck can take), which would make sloping the pipe in the installation easier - if you've ever worked with coiled pipe you'll know what I mean.  One issue I have is that the welding process leaves a slight bead on the inside of the pipe - this will collect water and be a place for the formation of organic matter, defeating to a small degree the slope to a collection well.  Of course, solvent-welded (glued) pipe will also have small grooving effects at the joints.

New Comments June 2012:
We didn't end up installing an earth tube due to costs and complexity, but also because enthusiasm for them has declined a bit.
In addition, the risks of earth tubes are not zero, though some say they are fine.  Have a look a this article:

Kitchen Range Hood

Kitchen Range Hood:
The HRV system is exhausting 150 to 200 cfm of air, which has already been dried to some degree after giving up its heat to the incoming airstream.  Someone has suggested using this exhaust as the make-up air for the kitchen range hood.  Seems like a good idea to me.  I would think one could get decent results with about 150 cfm, though some range hoods are rated 300, 400, even 600cfm.  We have a Sakura range hood in our existing house (600cfm).  If you need a high-performance range hood without the ridiculous high costs, the Sakura is the best we've found.  For about $300, you get a dual fan, dual motor high-performance unit with turbine-style impellors and grease collection at 4 points.  Four grease cups to clean, but no filter.  It beats the pants off the pretty stainless units costing $1500 or more.  We've had ours about 20 years without a single failure in daily use.  Make sure you install it with the recommended 7" duct.  We do lots of smelly cooking and frying, and I find the range hood never needs to run both fans, it is that powerful.  Each fan has two speeds, and it seems running one fan at low speed is adequate for all our cooking.  This could be about 150cfm.  A lot of the $70 range hoods are running at 60 to 80 cfm.  

A duct with a 3-way shutter could be used to redirect the HRV exhaust to the kitchen stove.  In the normal position, the shutter directs HRV exhaust air out of the building.  In the other position, it directs the air to the kitchen stovetop.  I plan to provide a stainless long and narrow rectangular register close to stove-top height on the backsplash.  Note the air temperature could possibly be a bit of a heating demand issue.  Some way of equalizing the flow rate of this make-up air with the range hood exhaust flow rate is also an issue needing attention.  The next challenge is the ducting needs to be valved (shuttered), and an insulated, fire-rated valve may be needed in the grease-laden exhaust terminal at the end of the kitchen range hood duct.  (Otherwise air is leaking out of the kitchen range hood all the time) The insulated valve should be electronically controlled and interlocked to the range hood operation (I would think preferably with low-voltage, say 24VAC, to reduce the possibility of sparks in the grease-laden exhaust duct.  A hand-operated mechanism with spring return could further reduce the chance of sparks, though I imagine operation may not be as convenient.
One more issue is that we plan to have more than one kitchen in our house.  This presents another challenge, assuming the HRV flow rates are indequate for both kitchen range hoods to operate at the same time. - The best option might be to provide a dedicated 2nd earth-tube for the make-up air.  another option might be to boost the HRV system flow rate with a booster fan.  We've been considering a 2nd earthtube as well, though I think this is extreme - the cost of the earthtube right now seems high -see the coming earth tube article.  And the 2nd earthtube would need to be placed far enough from the first to avoid a degradation in soil-to-air heat exchange.