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1/10/11

ERV vs. HRV For An Energy Efficient Prefab Home

Well. There I was nostalgically musing on how my prefab home packing had changed, readying for the next off grid zero energy prefab house kit weekend, when... Saturday morning: we awoke to snow.
Eh. Sorry guys, but I'm just not in the mood to schlepp out to the zero energy prefab just so we can get covered with icy mud and slush. Again. With colds. We've been doing a lot of that lately...

Instead, it's a good weekend to stay here and do sexy chores, like: order our shower head for the prefab!
WHY IS THIS EXCITING?
Because, for over a year, when we have "get things ordered and done" days like this, I have asked, "Should we order the shower head?" and Handsome Husband has immediately rebuffed, as only Germans can do, "Ach, NOOOOOO, ve are not at zat point in de projekt!"

Today, he blithely responded, "Sure, go ahead..."
WOW, we are at Zat Point in De Projekt!!!
So, honeychiles, I ordered a water-conserving, efficient Oxegenics Skincare Showerhead.

Also, after at least a year of debate,  I wanted to pass on what we decided for our own family regarding Fantek vs. Ultimate Air: (and ERV / HRV)
NEITHER!

PRESENTING...


Honeywell's TrueBREEZE HRV!

Here's why it took us so long to make a decision:
THE SUBJECT IS FRICKIN' FRUSTRATING:
The entire subject of HRV / ERV selection is nebulous. Passive House standards (PHIUS) push the Ultimate Air ERV, but ... we still had questions.

The dessicant wheel is a high maintenance item you can't even look for or access information on as a feature; and most people confuse an HRV / ERV with the method to ADD air to a house that, in our case, is being de-pressurized by a chimney... (Whereas you might choose to not add such penetrations in your prefab home, which will make it easier for you!)

First you look at what is an HRV, what is an ERV, and decide what is best for your particular conditions. What gets interesting is maintaining humidity, and its effects - that piece is not well understood, and there is simply not good information available out there.  You have to look at the facts- our house was so air tight our house priority is to get fresh air exchanged while then we drilled holes into that envelope that allow freezing air in (the chimney, penetrations this fall)

Handsome Husband Explains: "Why do we need ventilation? An airtight building is just that - air-tight. Well, MORE air-tight than conventional leaky construction. So much that the indoor air quality deteriorates to the point of becoming unhealthy. So we need to bring in fresh air (and oxygen). The simplest way to do this is to open your windows. Unfortunately this becomes impractical because in the summer you are letting in humid air (depending on where you live) and in the winter you let in cold (potentially VERY cold) air. Plus you have to listen to the distant dissonance of architects shrieking somewhere.

So you want to retain as much of the heat and/or level of humidity - depending on where you live - as possible.

Recovery Ventilators rush to your aid - the Heat Recovery Ventilator or HRV handles just that - heat from the air being exhausted from the structure is passed to the air being sucked in to the structure. Think about mixing hot and cold water - you get a temperature somewhere in the middle between the two meaning that the incoming air will have SOME of the heat of the outgoing air. This means that any use of an HRV will introduce  relatively cooler air into the house than the air that we just heated with our precious solar system. Since a warm house does us no favor if we don't have fresh air while we sleep we need to understand how much air we need to introduce i.e. how often and at what speed we run the HRV.

The Energy Recovery Ventilator (ERV) also maintains humidity i.e. it does not humidify or dehumidify the air - it attempts to maintain the level of humidity the same as the HRV attempts to maintain the level of temperature.

In the end, for our own purposes (we do not have air conditioning, or dehumidifiers, and are in the foothills of Virginia), we leaned towards the HRV because you can't use an ERV to suck air out of a bathroom - it would pass the humidity from the bathroom to the incoming air - which is what it is intended to do. ERVs treat moisture the way an HRV treats heat - they recover it. The alternative of a bathroom vent wouldn't work as we obviously  can't hook an exhaust fan in - it would depressurize the house."

Copeland Yanks Back Her Blog, Back To HERSELF, In HER Voice:
(Shakes hair, smooths it, then coughs discreetly to continue:)
Ahem. We sat down with James River Air, HVAC specialists in Richmond, whom I have gotten to know through professional and cultural overlaps, including Richmond's Green Drinks, which I co-organize.  James River Air's business model is steeped in the efficiency of HVAC, and, talking with them about our own particular site needs, decided instead to get the Honeywell HRV – a Honeywell TrueBREEZE.

Oh, and if you are considering using an ERV in a hot, humid climate like Virginia can be, you might want to  read this: "Use And Misuse of ERVs in Hot, Humid Climates."

Warning: The following is going to sound like an unabashed and gushing endorsement of a local business, James River Air. It is: : )
James River Air rocks.



Here, their esteemed President, Hugh Joyce, discusses reducing reliance on fossil fuels:




And finally? I'd like to pass on this gem, just for us all to consider:
The average German household today has 60.000 euros in savingsThe *AVERAGE* household. That's like... $85,000.
What are you *doing*, USA?!? 
http://bit.ly/gEl96U #WeSpendAndWaste
Handsome Husband and I had a good discussion on this article. On one hand, most Germans do not own their own home. So when you look at the equity of investments.. yet most here do not have that amount invested...

I know it seems like no one ever has two nickels to rub together, but... we need to evaluate our lives more. It's healthy to ask, "Do I need that? Actually, do I really even want that? How much more fun is it to instead save?" Saving doesn't always mean deprivation.

These years of The Land, we cut back on what other people thought was 'normal' to go on with our Great Plan for The Land.
Growing your own food in your own back yard saves money. Balancing what you think you need (A nice car? Regular dinners out? Beer? Well, never mind, beer IS necessary) and what you don't know yet that you could do without or create yourself... while allotting investing in expertise and knowledge... it's a hard balance of knowing which corner to cut, which area to invest in so you know it works, and is solid.
http://prefab-green-home.greenmodernkits.com/2008/09/prefab-green-building-house-kit-budget.html

I end this with love, hard work, and beauty:
[Via my talented artist friend Catherine Brooks. Cool, Catherine, thanks for sharing.]


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