[GSBN] Can bale buildings be air tight?- How to ventilate

Fri Mar 15 10:11:26 UTC 2013

Hi Graeme

I agree with this too. I understand the passvihaus drive to get us to use less and less fuel to keep ourselves comfortable. But I think we are straying way off the mark when we need complicated mechanics (driven by electricity) to achieve a "normal" level of comfort. And I worry too about how many petro-chemical based products (full of toxins and embodied energy) are used to achieve this.

I also worry about this (consumer-led?) expectation for everyone in every corner of the world, in all our different climates, to have a homogenised standard of "comfort". I like the fact that we have different seasons where we live in Ireland. I like the fact that we batten down the hatches winter and blossom again in Spring. I don't think it's environmentally-friendly to expect to be able to wear a t-shirt in my house on the coldest, dampest day of winter - because then I will have become completely detached from my environment. 

When we built our cob and timber-frame/straw-bale house, we made some decisions that forced us to work with nature. For example, we designed our rainwater collection tank quite closely to our water usage needs (we don't have any mains back-up). This ensures that the water is used and replenished regularly and we avoid the need for a complicated ozonator to combat stagnation. But it also means we are very aware of our rain patterns and how important that rainfall is. Even in saturated Ireland, we can get our dry spells. And when our friends lament the arrival of rain after a dry patch, we rejoice. Because when you realise you depend on rain, you don't see it as a negative that stops you going for a walk of makes the grocery shopping a little more uncomfortable. You realise how necessary and wonderful it is. The same is true is of our fuel. We hand-feed our stove with the left-overs from the carpentry side of our work. It is free - so we don't get a big, surprise fuel bill. But we have to work hard to chop that wood - we really appreciate its value and we physically see how much wood we are using (and can calculate how much more physical labour we will need to put in to keep our supply up). So much of this physical or practical engagement with the environment around us has been lost and I don't think that is a good thing. So many people have no idea where their water or heating or even food comes from or where their waste goes to. This disengagement with nature is not a good thing. And I worry that passivhaus possibly encourages a little more of this type of disengagement and promotes excessive expectations of controlled comfort.

I also think the simplest unmechanised solutions work best. I worry about the idea that we would need to get our house "serviced" every year in order for it to be safe. In Ireland, we had to bring in the National Car Test to force people to service their cars. I don't know anyone who services their boiler annually (as recommended). It's human nature. People won't service their MHRV systems and won't understand the consequences if they don't.

I don't have the answers. I know that research has been done about the ability for earth to absorb toxins (if anyone can point me towards actual papers on this, I would be very grateful). And considering that the earth itself will not be off-gassing anything noxious, it makes sense that this is a good route to explore the control of indoor air-quality. If the building fabric itself can actually pull the toxins out of the internal environment, then less ventilation will be required to control this aspect. I also am aware of research done by Dr. Paul Jaquin of Bath University looking at earth's ability to buffer humidity. Again, if we can control the RH in an enviroment and get it down to optimum, we will feel more comfortable at lower temperatures - i.e. we need to burn less fuel. 

There needs to be a balance between reducing our energy usage, but by simple, fool-proof, non-toxic methods.

Having said all that, I also have a question about sealants for windows. Has anybody any experience of using oakum, pine pitch with hemp fibre? If so - how did it work for you? I'm looking for ideas on natural, breathable sealants.

Thanks (and sorry for the rant)

Feile

Féile Butler

MRIAI B.Arch Dip. Arch Conservation Grade III

Mud and Wood

Grange Beg, Skreen, Co. Sligo, Ireland

T:  +353 (0) 71 930 0488 

M: +353 (0) 86 806 8382

E : feile at mudandwood.com

W: www.mudandwood.com

----- Original Message ----- 
  From: Graeme North 
  To: Global Straw Building Network 
  Sent: Thursday, March 14, 2013 10:51 PM
  Subject: Re: [GSBN] Can bale buildings be air tight?- How to ventilate

  Well my 2c worth is that in NZ we have a long history of cold damp houses, in a very humid mostly temperate climate.  (As it is at the moment we are in the grip of the worst drought for over 70 years so any hint of damp would be welcome.) 

  That aside - the best strategy I have found for drying out damp houses is to use hygroscopic materials in the fabric of the house - and the best and easiest is earthen walls or at least earthen plasters on any suitable substrate such as dry wall.  Of course to help get over cold we insulate and that's where sheep's wool, or strawbale,  or low density earthen materials, come into their own.  Condensation on windows and the accompanying wet window sill syndrome simply vanishes.  Needless to say we don't have several cm of snow lying around but we do get some pretty good frosts.  Then reducing the size of houses and the size of windows in them also helps. Lets face it, oversized badly orientated triple or quadruple glazed self ventilating thermally broken windows are still not nearly as good as a bit of well insulated wall at keeping heat in or out.  

  I suggest that the approach of using more and more of the earth's resources to sort out these building issues  may not be a good primary design strategy, especially when it leads to oversize buildings, with oversized windows needing mechanical ventilation systems etc., -  mechanical systems that are only as good as their energy supply.  I don't want to wake up dead of asphyxiation in an air tight building because the electricity failed while I slept.

  This is not to dismiss some very good building science and its associated research, but I am finding this conversation on interior air quality in air tight buildings a bit disturbing when we end up with buildings so tightly sealed that the occupants are at risk from either the building fabric itself, or even more alarming, from their own breathing!   People would be much healthier outside the building under these circumstances.  Interesting, isn't it, how, if a person feels ill we often take them outside, where they usually feel much better?  We really do need protection from the built environment.  

  I prefer a design approach that minimises the use of expensive, resource gobbling, and complicated materials and systems.  A colleague of mine sums it up thus:
  The.... division is between those who fling open their doors to embrace the day, and those who huddle behind triple glazing worrying whether they are going to be comfortable.   Tony Watkins FNZIA 

  Graeme "Stirrer"

  Graeme North Architects
  49 Matthew Road
  RD1
  Warkworth 0981

  www.ecodesign.co.nz

  On 13/03/2013, at 5:04 AM, RT <ArchiLogic at yahoo.ca> wrote:

    Tony wrote:

      Is there a window sill detail for the interior that could accommodate the inevitable moisture present?

    Carolyn wrote:

      "ventilation window" ...two glass panes with space in
      between - like 3-4 inches.

    Tony;

    Condensation on glass and subsequent puddling on window sills would of course, best be addressed at the source of the problem (in most cases just providing proper ventilation) but for small amounts of water accumulation, a gutter detail can be useful.  In the commercial window industry, the aluminum extrusions (especially with sloped glazing) typically include a condensation gutter.

    For residential windows it would be a matter of bending some corrosion-resistant sheet metal flat stock to mimic the profile of the sash and glass stops of the bottom rails to function as flashing to direct the runoff into a collection gutter which may be integral to the flashing or a separate piece of off-the shelf stock (ie J-trim ).

    Also, for the sills themselves, tile or stone set in a mortar bed rather than a moisture-susceptible material such as wood.

    Carolyn;

    I don't see a file attachment for the windows you mentioned but they sound like the "laminar flow" windows that were marketed over on this side of the pond in the early 1990s.

    My objections to them back then were:

    (1) Solar pre-heating of ventilation supply air by the windows would only be happening when the sun is shining and striking the equator-facing glass.

    In winter, at my latitude here near Ottawa, Ontario Canada that would be be limited to effectively about the 4 hours around 10:00 to 14:00 hrs.

    Problem is, in most normal households, there is no one home during that time.

    "Okay, so we'll just store that fresh air inside until people get home to use it. Right ?"

    I don't know if Denmark has ventilation requirements written into the Code but there are minimal flow volume guidelines in existence intended to ensure good indoor air quality (see handbooks put out by ASHRAE or IHVE etc).  These, like building codes are minimal standards intended to provide a minimum level of health safety. I assume that we on the GSBN list aim higher than the worst buildings allowed by law.

    Here in Canada we've had considerable experience with trying to make well-insulated buildings and learned very early in the process that making such buildings air-tight was an absolute necessity and of course, the corollary being that proving an effective ventilation strategy is also absolutely necessary and the R-2000 program from the early 1980s taught us many lessons that are still valid today.

    The PassivHaus standard utilises most of the same principles (with some variations on targets) but PH strikes me as being confused so I won't talk about it here.

    The CAN/CSA-F326 Standard (first published in 1989 and revised in 1991) is one of most comprehensive available on the subject of ventilation requirements and it lists the following:

    ==============Copied material =================
    Table 1. Ventilation Capacity

    Room Capacity, L/s
    Master bedroom 10
    Other bedrooms 5
    Living room 5
    Dining room 5
    Family room 5
    Recreation room 5
    Basement 10
    Other habitable rooms 5
    Kitchen 5
    Bathroom or
    water closet room 5
    Laundry 5
    Utility room 5
    =================== end of copied material =================

    In 1994, a study was done for the Energy Efficiency Div., Residential Program, Energy Technology Branch CANMET, Dept of Natural Resources Canada (now NRCan)

    "Indoor Air Quality and Ventilation Rates in R-200 Houses"

    which found that most owners of R-2000 certified homes were operating their heat recovery ventilators (HRVs) at 75% the rate specified by the F326 Standard with no deterioration in IAQ and recommended that the lower rate be adopted for R-2000 certified homes.

    Recently on the Greenbuilding list in a thread on the topic of ventilation, WatJohn mentioned some similar numbers (ie lower rate than those specified by F326) as a guideline:

       (per WatJohn)  7.5 cfm (~3.6 L/s) per occupant + 0.1 cfm per sq foot floor area

    ... which, if you crunch the numbers will yield a "NO!" to the question posed (re: storing solar pre-heated fresh air) -- the point being that depending upon the degree of air-tightness of the building, there are certain minimal ventilation requirements that must be met or there will be unacceptably high levels of pollutants which will have deleterious effects on the health of the building's occupants.

    Condensation on windows is just the most visual and most easily-addressed indicator that the house is suffering from poor ventilation.  It is the "invisible" pollutants that are more worrisome -- CO2 and VOCs.

    The other thing that is troubling (to me anyway) is that we're only just now having this discussion on this List when the resources to address these questions have been readily available for the past three decades or so, pretty much pre-dating the current "SB Revival".

    The need for air-tight construction with well-insulated buildings and the need for effective ventilation strategies for air-tight buildings does not have one set of requirements for buildings made of conventional materials and another set for buildings made of natural materials simply because the natural processes involved don't make the distinction.

    That is to say, since the resources to address these issues already exist and these days are quite likely accessible with a few mouse clicks, there is no need for willful naivite or missions to re-invent the wheel. It's okay to transfer that knowledge to SBC and NatBuild.

    No doubt there will be arguments to the effect "We don't want no stinking mechanical ventilation gizmos just so we can breathe ..." but that's a non-starter.

    What's necessary are the ventilation rates to ensure health.

    It doesn't matter how those rates are provided.

    In milder (than Canada) climates and smaller, single-storey homes (ie under 160 sq metres) exhaust-only/passive-inlet ventilation strategies (EOPIVS) are an alternative to HRVs. The downside to EOPIVS is that there will likely be no heat recovery capacity on the exhaust air stream which means that energy consumption for space conditioning will likely be up to 40% higher than it needs to be and for any building aspiring to be "Green" in 2013, is that acceptable ?

    But enough of that (and apologies to those who have had to endure this rant on numerous occasions previously).

    -- 
    === * ===
    Rob Tom AOD257
    Kanata, Ontario, Canada

    < A r c h i L o g i c  at  Y a h o o  dot  c a  >
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