RE: HRV Ventilation (edited post with added photos)
RE: HRV Ventilation (edited post with added photos)
Ventilation will be this fall's project. What model HRV did you choose? Why did you go with a HRV vs. an ERV? We live in similar climates, so I look forward to hearing your insight on that aspect of your build. Thanks in advance!
Haffs (and noted for others)
Although I did respond to your questions about HRVs and ERVs, in re-reading the thread post there were some important points that I thought were important, (plus some poor writing - hey I am sorry I am an engineer, not english major), so I re-edited the post and uploaded to my web site along with a few photos. Debated whether to repost the entire thing or just link to site. As many may not visit other sites, I shall repost here and add the photos.
For general understanding for those not familiar with HRVs:
What is an HRV:
An HRV (abriviated for "ลHeat Recovery Ventilator"ย) is installed as a full house (or building) mechanical ventilation system that operated continuously (all year & 24 hours/day) at a low volume (typically 100 cfm in smaller homes to 300 cfm in larger homes). Its usual purpose is for bringing in "fresh" air and exhausting "bad" or contaminated air as close to the sources as possible (like bathrooms, laundry rooms, kitchen areas). There are commercial HRV/ERVs but discussions are beyond the scope of this post. They are also used for some other specialized purposes such as in high humidity areas (pools, spas, aquariums, finger nail finishing studios or hair dressers, manufacturing processes, etc.).
HRV Systems:
I use to design HRV systems, as well as sold them for a number of years in Canada where they are used a lot more in home construction. Each situation should be looked at individually and appropriate selection and its installation design because these units are of lower velocity/air flow and aspects of ductwork lengths/sizes and elbows can greatly influence performance.
As for aquarium applications, what typically works for sizing for normal applications in houses, goes out the window, due to continuous excessive moisture generation from things like open surface water tanks and moving water. So "rules of thumb for HRVs" do not apply.
It was asked the difference between selecting an HRV (Heat Recovery Ventilators) vs. ERVs (Energy Recovery Ventilators):
Mechanically HRV and ERV units are typically the same, in that they bring in "fresh" air from the outside and exhaust "poor" air from the inside and do so by passing the two air streams by one another in an internal "heat exchanger" that does not mix the two air streams. It works like the radiator of your car, but instead of water and air, it is an air to air exchanger.
Photograph of the Interior of a Heat Recovery Ventilator (Dual Core 300 cfm)
The primary difference is in the "core" or "heat exchanger" which is constructed of various materials. Some are thin metal (aluminum or galvanize) or plastic which do not allow a transfer of moisture through the material and these are used in HRVs. ERVs on the other hand utilize a cloth or paper material that do not like the air streams mix as the air passes through the exchange transferring heat (tempering the air temperatures), yet in addition, the cloth or enthalpic core, also allows for the transfer of moisture between the two air streams. The moisture transfer may be good for homes in areas where you want to maintain or increase moisture levels (in the range of 35%-45% RH) of a home, particularly in colder climates in the winter and houses with hardwood flooring. So ERV are appropriately selected. There are other factors too for selecting ERVs too and advise those thinking of units to contact the technical department of HRV manufacturers like Fantech.net (Bernie is a good tech to speak with) to learn about the one best suited for your application.
Photo of a HRV Dual Core (more energy efficient - double by-pass)
Check Out Specific Unit "โ Most units not suitable for Salt Water Environments:
Please note: There are different styles of HRV/ERV (rectangular cores, drum wheel types) produced by a wide variety of manufacturers (Fantech, Venmar, Vanee, Lifebreath and many more). Definitely contact the manufacturers' technical department directly (as opposed to the distributing seller or sales person) when choosing a unit that it can handle salt water environments otherwise the unit may rapidly deteriorate, rust, electronic controls fail or adversely affect the fans or motors. Also find out about the necessary routine maintenance required, especially for salt water air.
PURPOSE
In the case of a high humidity generation and corrosive contaminated air like a salt water aquarium, we wish to expel the "bad" air from the source and do not wish to typically keep moisture within the space.
Therefore, it is in MY opinion for MY application, I wish to utilize HRV which remove the moisture laden air from the interior without an enthalpic core to bring up the moisture content in the air being returned into the environment. Your situation may warrant differently.
Units Chosen:
I choose to go with two additional HRVs dedicated to the aquarium system (one has been operating in the home since it was built 10+ years ago), each with dedicated ductwork for exhaust locations and fresh air return supply back to these areas for balanced ventilation. The two selected units are:
(a) The main display tank area: Fantech (140 cfm) HRV
- venting the hood enclosure
- the underside cabinet because of through floor piping could not be sealed to the crawl space below
- around the entertainment centre as it is close to the tank
- and an extra lead for possibly for a smaller minor display tank
(b) The Aquarium Room and Filtration Area: Fantech SHR 3000 (300 cfm) HRV
- venting exhaust registers over open water sumps/tanks and the service/cleaning sink and where the closed loop pumps are. Each with in-line duct dampers for balancing and adjustments
- fresh air supply returns to opposite sides of exhaust to force air movement across the areas
Important or Notes to consider:
Treat as a "ลwhole ventilation system of integrated sub-systems or components"ย which requires that the room be isolated, ductwork designed appropriately, outside intakes and exhausts located correctly, the controls located and programable as you desire, the HRV unit is sized correctly, and is balanced after installation (an important step).
The trick to making things work is to isolate the areas with a continuous vapour barrier system. In my case I used double-bubble vinyl vapour barrier and a series of heavy gauge plastic drop walls to prevent dissipation or migration of moisture into the wood joist area, other basement areas or elsewhere in the home. Without the areas being air tight, sealed and isolated to effectively draw the moisture from the sources, the ventilation system won't work effectively and can result in building moisture problems (e.g. Mould, accelerated deterioration, destruction of plywood sub-floors or drywall, wood rot, etc.)
Two things are critical and you should take into account: the proper ductwork sizing; and the balancing after installation which refers to the balancing of fresh incoming air equalling that being exhausted (is important so the isolated rooms or areas are not positively pressurize, potentially forcing moisture laden air into walls and floor cavities.
Know how you would like to control these units which have multiple fan speeds for varying the air flow which can be controlled manually, programmedd and even set on humidistats.
Another note, like your pumps and lights, these take energy to run. Check out the energy to run the unit as it does operate 365 days a year for years. Typically, in our area (your local climate may vary) a HRV can run about $200 to $350 per year to operate.
Hope that helps.
Joe
good luck, I'll be following your thread. But the earlier stated question how you plan to do water changes and maintenance would be interesting for me. 
