Ok, so if you put in radiant, what do you do with the "VAC" portion of HVAC? Radiant is expensive as is, but now you're also running expensive single-use ventilation all over. We are in Zone 5; mostly heating. The house will be 'tight', so perhaps SIP. What's the most cost effective way to provide ventilation and/or A/C. ...meaning, A/C is optional..but since you have venting pipes, may as well slap on an A/C unit, no?

"V" isn't hard to do with a dedicated ventilation system. Ducts are much smaller than for AC. Energy use can be as low as 40 watt continuous with a good ECM fan unit.

if you want AC, that depends on many things. what's the heat source?

Does 'V' use the same tubing as 'AC' if we use mini-duct for example? Heat source for the radiant? Mod-Con boiler seems the way to go...to get the DHW use out of it as well.

you wouldn't use mini tube for just ventilation, it would be a huge expense and lots of wasted energy for no additional benefit.

For AC, most people would upsize the ducts for an air system if they wanted cooling, or do independant heat pump cooling units in some key rooms.

we're starting to play with radiant cooling, but it's pretty brand new to residential.

I should have asked, what's a good (online) source of HVAC fundamentals with lots of diagrams? :) I could really use a better understanding of ducts/venting. The heat and A/C stuff I generally understand. But what are all those crazy ducts and pipes doing up there? ha! how and why are they layed out?

Energy Recovery Ventilator

My house energy rater said all I need is a high efficiency vent fan on a timer and a fresh air supply, to satisfy air change requirements in my tight house (don't know exactly how tight, until I get the blower door done). The only duct work I have in the house is that going to the bathroom fan, the kitchen range vent, and the Panasonic FV-13VKS2 vent fan I am using to provide air exchanges for the whole house. In other words, just a few feet of duct work total. After going to all the trouble of avoiding a heating system that uses duct work, it seemed insane to me to add an HRV or ERV system that needed all the duct work I was avoiding.

For fresh air (and summer cooling) I am using windows, but then I live out in the boonies with great air. I am also in Zone 5 and we don't need air conditioning. I am building a solar preheat box for the winter fresh air intake. I do like to experiment, so give me a year and I will tell you how it all worked. In addition I am not going to sell this house, so resale value is not a concern for me - a luxury many folks don't have.

-Rosalinda

You can satisfy raw air change requirements that way, but you cannot ensure good air quality in various areas of your home that way. that requires dedicated supply to target areas, and attention paid to airflow through the home.

It also does not meet ASHRAE or Canadian standards that way, which all prescribe flow to each area.

That would be satisfying the letter of the law, perhaps, in your area. but it does not ensure health.

I can see your point Rob, but we are only talking 3 or 4 months of the year this artificial system will be needed. I do have the appropriate venting to bath and kitchen, and the make up air source, in addition to the vent fan. There are only 2 sources of combustion in the house, the hot water heater, which has its own air supply, and the kitchen range. I monitor humidity and use a dehumidifier as needed, (the house is new and still drying in) and have lots of house plants that reside inside in the winter months. The house is on a very open plan, so I am convinced all will be well. In truth I can't see that air quality will be an issue, but live and learn.
-Rosalinda

So you're not concerned with good air quality for 4 months a year? Heck, you only need heat for that amount of time too, just put a pellet stove in the middle of the house and call it good! That's an awful long time to hold your breath...

google "sick house syndrome" sometime. I have no idea how many modern asthma cases are the result of poorly ventilated spaces... but I am not at all shy about saying "lots". And that's just one of many, many problems associated with poor air quality. Combustion is not the primary concern. there are many, starting with the existence of respiration (people), offgassing of components in the home, etc.

If your incoming air does not need to pass through a room on its way to an exhaust then that room will likely not be properly ventilated. This is not good. You might mitigate any moisture/mold issues at least because vapor pressure will balance itself out, but that does nothing for the sea of pollutants in normal day to day living in a tight environment.

I myself have a wide open office with a small server room WITH NO DOOR off in one corner. the server room has no fresh air supply or exhaust, but the open doorway is almost 1/3rd of the wall area between the two rooms. I am exchanging plenty of air in the main area. Yet, you can still smell all the paint in the server room (low VOC, even) a year later. I assumed it would mix and be fine. I was wrong. If we spent any amount of time in that room at all I would retrofit a supply air port in there immediately.

I am convinced all is not well without proper attention to where the air is going.

Mini-duct setups are more expensive than traditional ducts? However, mini-duct seems more DIY friendly, true? I like the mini-ducts low space requirements for sure.

Posted By NRT.Rob on 09 Feb 2011 02:26 PM
So you're not concerned with good air quality for 4 months a year? Heck, you only need heat for that amount of time too, just put a pellet stove in the middle of the house and call it good! That's an awful long time to hold your breath...

google "sick house syndrome" sometime. I have no idea how many modern asthma cases are the result of poorly ventilated spaces... but I am not at all shy about saying "lots". And that's just one of many, many problems associated with poor air quality. Combustion is not the primary concern. there are many, starting with the existence of respiration (people), offgassing of components in the home, etc.

If your incoming air does not need to pass through a room on its way to an exhaust then that room will likely not be properly ventilated. This is not good. You might mitigate any moisture/mold issues at least because vapor pressure will balance itself out, but that does nothing for the sea of pollutants in normal day to day living in a tight environment.

I myself have a wide open office with a small server room WITH NO DOOR off in one corner. the server room has no fresh air supply or exhaust, but the open doorway is almost 1/3rd of the wall area between the two rooms. I am exchanging plenty of air in the main area. Yet, you can still smell all the paint in the server room (low VOC, even) a year later. I assumed it would mix and be fine. I was wrong. If we spent any amount of time in that room at all I would retrofit a supply air port in there immediately.

I am convinced all is not well without proper attention to where the air is going.

Rob - its nice to see a professional that actual understands the need for proper ventilation. So many times (even on GBT) we see comments like "I don't need to ventilate, my humidity is already way down" or " If you are that dry, you are over ventilating." People need to understand that here are a whole host of health concerns associated with new tight houses that all have their root in poor ventilation. Its a little like saying "its okay to piss in the pool as long as you don't crap." If you don't see the pollutants they don't exist. Vent it right and than add or subtract humidity as needed. Apart from offgassing of products we build with and products we use in the house, we also have to vent in ratio to the amount of people per cubic foot. If there is only two people living in a big house there is a lot more leeway than if a family of five live in a 1000 sq. ft. house. I do think the mini duct systems cost more than they should, (I have one and would probably not do it again unless the prices come down)

Posted By NRT.Rob on 09 Feb 2011 02:26 PM
I do think the mini duct systems cost more than they should, (I have one and would probably not do it again unless the prices come down)

why is that, just because of cost or does it have issues? could you put the cost specifics (vs a regular ducting system if possible)

that quote says it's from me, but it's not (we don't have a mini duct system). My problem with mini duct systems is that I believe they use significantly more power than a properly designed conventional system to distribute the air.

Nice rant Rob , I will keep all you say in mind and make sure the air intake is providing fresh air where it is needed, when it is needed. I am just not satisfied with the current choices of ERV and HRV ducted systems. Maybe someone will invent something better. I have seen wall mounted units that duct directly through a window or a hole in the wall, that use electric to preheat the fresh air. At present the idea of adding more electric load does not interest me, but if photovoltaics become more affordable, it might make something along those lines more feasible.

-Rosalinda

I love it when people make stuff up. But you tried Rob.

An ERV is state of the art, I won't go into to the details because I haven't Rob's patience.

Suffice to say to those that will listen, when you build a tight energy-efficient house, you have to have one to control the flow of fresh air, humidity AND recover the energy you use to to condition the space.

Open-window conditioning is for renters.

You can run an ERV that is more than 90% efficient sensible and over 50% latent transfer for 40 watts of power, and get MERV 12 filtration to boot. Passive Houses use them, that's a pretty good endorsement in my book.

Hey, you guys give really good advice and I appreciate it. You are knowledgeable, up on the technologies, and willing to share with the rest of us. It is why I and others come to these boards. I always take what you have to say into consideration, but when applied to my own situation it might not always fit. That doesn't make me an idiot, nor does it make your solution the only one possible. I will keep asking questions and questioning answers - it is how I learn- and I hope you all keep answering. There is plenty for folks to learn in the discussion, despite how thick one might think the other party in the discussion.

-Rosalinda

I find many people on my side of these discussions simply get fatigued being confronted with the same misunderstandings for years, and years, and years. pay it no mind: it's annoying when you know better but don't see things changing, but that's not your personal fault. I myself am astounded that 30 years into efficient building I still run into PROFESSIONAL BUILDERS who don't understand the need for IAQ control.

I happen to be a particularly tenacious debater, so I don't tire easily

You're right that the "stock option" doesn't fit everyone and you definitely need to think for yourself. But I haven't seen too many floorplans that could easily vent with just a central exhaust or supply fan that didn't include airlets through the walls (controlled leakage). So I don't know how you'd address this issue without at least a few ducts. But I've been wrong enough when applying "general standards" to particular individuals that I don't always assume there isn't an exception. But I do have to reiterate: the server room example really blew me away. prior to building our shop I would never have assumed that airflow in that side room would be so negligible or ineffective, open as it is to the main office. It was eye opening for sure.

Best of Luck!