You could do something like the Vents Micra 60 or Lunos instead of a whole house solution. I'm assuming the Panasonic spot ERV will not work for you because of climate.

Interior humidity control is definitely a consideration. But wood burning stoves tend to take care of that.

I don't think we need an ERV because we definitely don't need air conditioning here.

Patonbike, thanks for reminding me about those...I had planned to look into them.

Given it is such a small window of time in the course of a year when the house is really going to be sealed up, I'm hesitant about spending money on fancy and expensive systems.

The house is only sealed up for about 3 months of the year...can get by with exhaust-only ventilation.

If that's what you want to do, have it tested to make sure you actually get the ventilation rate that is needed for a healthy indoor environment - in each room, under all conditions.

Wood burning stoves with outdoor air supply do not dry the air any more or less than other forms of heating.

Posted By walleygirl on 27 Jul 2015 01:42 PM
Interior humidity control is definitely a consideration. But wood burning stoves tend to take care of that.

I don't think we need an ERV because we definitely don't need air conditioning here.

Patonbike, thanks for reminding me about those...I had planned to look into them.

Given it is such a small window of time in the course of a year when the house is really going to be sealed up, I'm hesitant about spending money on fancy and expensive systems.

Wood burning stove neither add or remove appreciable amounts of moisture from the air, even when drawing combustion air from the conditioned space driving infiltration. 

The tighter the house (or the lower the ventilation rate), the higher the indoor humidity will be.

Hmmm, must be an anecdotal thing then. Every home I've been in where they have a wood-burning stove is noticeably drier, and the owners have said as much (humidity is a big issue here in the wintertime, as the outdoor air gets pretty humid as well). Maybe these houses are not sealed up very tight. Mind you, our current house (ancient crappy mobile that I can't wait to get out of) is definitely leaky, but indoor humidity is a big problem for us.

Anyways, all good things to consider, thank you.

Mine is not the tightest house on the block but getting tighter with every project. I've monitored indoor humidity for years, and (as expected) it did not change at all when we installed the wood stove a few years ago. It HAS changed measurably as we've tightened up the house, and we have now reached the point where active ventilation is required to keep the interior humidity lower than 40% RH@ 20C in winter.

Outdoor humidity (as measured by outdoor dew point) is still lower in winter in western coastal Canada and the Pacific Northwest than it is in summer, even on the rainy coasts. But it doesn't spike in summer the way it does on the right half of the the continent. It's (almost) always at a dew point low enough that the rising indoor humidity can be readily managed by ventilation rates, with rare exceptional days in summer. In winter the dew points are literally never that high. Ventilation air with a dew point of 3-4C is pretty comfortable & healthy when raised to an indoor temp of 20-22C, and that's the mid-winter average in Nanaimo. The mid-summer outdoor dew point average for late July / early August is still under 15C, which is somewhat humid, but not sticky-uncomfortable or unhealthy.

Pull up a dew-point graph:

https://weatherspark.com/#!dashboard;q=nanaimo%20bc%20canada

So, summer and winter the humidity levels of the ventilation air is usually in the "Goldilocks zone", and when it isn't you can adjust the ventilation rates to suit. In much colder or more humid climates winter air can be way too dry and summer air much too humid, with higher conditioning needs.

Posted By Dana1 on 29 Jul 2015 04:22 PM

Posted By walleygirl on 27 Jul 2015 01:42 PM
Interior humidity control is definitely a consideration. But wood burning stoves tend to take care of that.

I don't think we need an ERV because we definitely don't need air conditioning here.

Patonbike, thanks for reminding me about those...I had planned to look into them.

Given it is such a small window of time in the course of a year when the house is really going to be sealed up, I'm hesitant about spending money on fancy and expensive systems.

Wood burning stove neither add or remove appreciable amounts of moisture from the air, even when drawing combustion air from the conditioned space driving infiltration. 

The tighter the house (or the lower the ventilation rate), the higher the indoor humidity will be.

Not quite sure how those two statements can exist side by side. If a wood stove is drawing well and drawing from conditioned space, does it not mean that the ventilation rates increase?

Even a pretty big wood stove doesn't draw more than 10-20cfm for combustion air, and a smaller wood stove (or a big 'un throttled back) draws less than 10cfm. That's a pretty small relative to the normal ventilation required for human-healthy houses, but it would be enough for ventilation for a single bathroom if it was running 20cfm at 100% duty cycle for the whole 8760 hours per year. As a fraction of the whole ventilation it's a very small drying factor.

By contrast, open hearth fireplaces typically draw 50cfm+ even at low firing levels, and 100-200cfm+ is pretty common with a bigger fire.

Not exactly a scientific peer-reviewed but still semi-credible reference:

http://woodheat.org/the-outdoor-air-myth-exposed.html

Most homes without being tight and ventilated right suffer from air quality issues. You simply cannot control, dust, dust mites, pollen, temperature, humidity, Oxygen content, VOC buildup, local stagnation etc. without a tight envelope and controlled ventilation. It is required if you want a healthy environment.

Brian

I'd add CO2 and radon. Even leaky homes that might normally provide enough natural ventilation will have the ventilation rate drop below recommended levels during calm, moderate temperature periods. There simply isn't any pressure to cause air to move.

Posted By Dana1 on 05 Aug 2015 05:27 PM
Even a pretty big wood stove doesn't draw more than 10-20cfm for combustion air, and a smaller wood stove (or a big 'un throttled back) draws less than 10cfm. That's a pretty small relative to the normal ventilation required for human-healthy houses, but it would be enough for ventilation for a single bathroom if it was running 20cfm at 100% duty cycle for the whole 8760 hours per year. As a fraction of the whole ventilation it's a very small drying factor.

By contrast, open hearth fireplaces typically draw 50cfm+ even at low firing levels, and 100-200cfm+ is pretty common with a bigger fire.

Not exactly a scientific peer-reviewed but still semi-credible reference:

http://woodheat.org/the-outdoor-air-myth-exposed.html

Fair play for the other side http://www.chimneysweeponline.com/hooa3.htm

That link seems to support "outside air is harmless" vs "outside air is required/beneficial".

Whether or not combustion air "needs" to be drawn from the outdoors, the cfm rates for woodstove combustion air are very modest, and not a big drying factor in any house.

I live in the PNW. Designing a home in this area to work efficiently is not difficult. When summer time hot weather happens we have a diurnal temperature range that allows for night time cooling during these times and oppressive humidity is an extremely rare event here. If the home is reasonably designed, high internal thermal mass, tight, properly ventilation and super insulated there is no possible need for typical air conditioning.

Any code compliant home can be upgraded to a passive level performance for under $5 to $10 dollars per square. When you are paying $150 a square foot for the house or so that is less than 8% of the cost. The energy savings easily offset the additional mortgage expense for any upgrades. If you can not qualify for the extra mortgage reduce the size of the home by 8% with a little design optimization. A passive house is healthier, provides better long tem cash flow making you wealthier, and is more comfortable to live in making you more comfortable. It also eliminates worries of escalating energy prices for ever.

The only argument for not building to a passive level is that you plan on flipping the home and the energy hog you are creating will be someone else's problem eventually. The fact that we do not build all houses to a zero energy standard is appalling and can only be justified by business as usual, I do not care about the world, keep up with the Jones, Invest in pretty and size and not use or brains to educate ourselves and do the things that make the best decisions to improve our personal, community, country and world health and sustainable future.

PNW coastal areas have rain, drizzle, mist, dew, mildew, mold, salt spray (in coast areas), moss in forest area issues. Building a building that eliminates these issues is a good idea. Building low maintenance cost into the home material choices is also a great idea. PNW also has enough sunshine for solar thermal and PV and mostly cheap hydro based electricity keeping standard electric rates reasonably low at this time.

Providing piped outside air to any burning appliance is a good idea. Appliances that use internal air always pollute the indoor air to some degree. changing the balance of air flow in an HRV and or ERV diminish there performance numbers quite a bit as well.

Just a few related thoughts.

Brian

Thank you all for the information.

Right now I'm sitting at using minisplit heat pumps as my main heating source, with a wood burning closed fp or wood stove as backup. The point is to avoid ductwork.

So, can I mechanically ventilate my home without having ductwork? what options do I have?

No. Use mini 4 or 3 inch hdpe anti static small ducts for air exchange and distribution only. Place under insulation in roof cavity. No ventilation means an unhealthy home. Air exchange does not require high flow like a furnace. Typically less than 300 CFM. CFM is based on 3 exchanges or so per day in occupied areas. Ventilation should be based on air quality, humidity, VOC level, Oxygen level ECT. Standard exchange rates are based on occupancy, and air tightness but it is best to monitor air quality and ventilate appropriate to optimum health conditions for occupants.

Brian

A well insulated and well sealed house with a single (or few) point HRV/ERV and open interior doors.

This seems a bit crazy. Build up a house so tight you can't breathe without mechanical ventilation? Surely there must be a happy medium.

Can I put these ERV things in the bathrooms (we'll have 3) and be done with it?

Maybe I'll just light a fire every other day in the winter and throw open the windows. Good ol' fashioned ventilation! The wood is free, so it doesn't cost me anything. :-)

Not sure if I would place any ducts, mini other otherwise in the attic. They will definitely rupture the air barrier. It is almost sure that her code officials will require 6 mil barriers for her walls and ceilings unless she has a P. Eng. indicate they are not needed.
Duct work in and out of a ceiling diaphragm are much harder to air seal then pot lights!

Posted By walleygirl on 14 Aug 2015 01:07 AM
This seems a bit crazy. Build up a house so tight you can't breathe without mechanical ventilation? Surely there must be a happy medium.

Can I put these ERV things in the bathrooms (we'll have 3) and be done with it?

Maybe I'll just light a fire every other day in the winter and throw open the windows. Good ol' fashioned ventilation! The wood is free, so it doesn't cost me anything. :-)

"Crazy" is ventilating with random air leakage of unknown quantity, source, and path with the ventilation distribution in unknown and random amonts & locations.

Mechanical ventilation puts the ventilation where it's needed, in the quantity that is appropriate, and drawn through a known non-polluted, non-moldly pathways, and removing air from the highest-pollutant points.

You may be able to just use bathroom ERVs + kitchen exhaust ventilation if you leave the bathroom doors open.  But it may be worth doing a bit more.

Panasonic makes a single room ERV that is appropriate for in your climate, settable to flow rates appropriate for bathrooms.  (~$350-400USD from multiple online vendors.)

Lunos makes ductless HRVs that work in pairs at very high efficiency, which works great for the general ventilation in modest to moderate sized homes. You can add pairs if you need more ventilation. (SFAIK only available thorugh 475 Building supply in N. America, about $1KUSD/pair.)  These have been used as whole-house ventilation for PassivHaus-tight homes in Europe and the US (probably Canada too, but I can't point to a specific house.)

In your climate there is little rationale for ERVs over HRVs, since outdoor dew points are in a healthy & comfortable range for both the humans and the house 99.8% of the time, and don't stray in to a less-healthy range (on either the too dry or too humid end) for periods long enough to matter.  ERVs would be more appropriate in Florida or Alabama where the latent cooling loads are high, than British Columbia or Oregon, where the average latent cooling loads are negative.

Windows work great for ventilation, but don't conserve heat (or moisture). With HRVs you can ventilate at fairly high rates (much higher than random air leakage in typical houses) without much energy-use penalty.

If you're not contaminating the place daily with aerosol sprays, toxic cleaners, burning candles, incense,  or smoking stogies your ventilation needs are going to be pretty low- much lower than prescribed in ASHRAE 62.2, and a modest amount of exhaust-only ventilation would probably cover it (even without heat recovery.)