hrv in off grid home

alexis.marcil
alexis.marcil Registered Users Posts: 11 ✭
in General Solar Power Topics #1
Hello,

I am curious to see what people with off grid homes uses for ventilation. Do they use HRV even though they can use a lot of power or they simple ventilate and heat more?

thanks

Alexis
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
    Re: hrv in off grid home

    Not that we currently are living in an OFF GRID home but the plannning is progressing, all be it slowly... construction starts soon...

    A friend, on grid has an HVAC in his brand new house so I looked at the rating >> .9 A @ 110 V = +- 2.4KWH per day...Too much. He did tell me that the fan is 4 speed and he runs it at the lowest setting most of the time so it does draw less than that big still a BIG load.

    My preference after working in sealed offices for +- 30 years is to have windows that open..

    the need for an HVAC is to counteract the effect of the 'sealed' building so if a bit of fresh air can get in why do you need an hvac, also if you re burning wood in a unit that does not have a dedicated air supply you will have lots of (adequate) turnover.. the HVAC is needed to removed excess moisture 'trapped' in the house... windows that open are a great invention;)

    HTH
    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #3
    Re: hrv in off grid home

    We're planning a new build off-grid home in Spain that will comply with the Passivhaus certification for energy efficiency. This demands an HRV with heat recovery because of the high degree of airtightness in the building. The unit's I've looked at only provide ventilation and heat recovery, no active heating and they use efficient DC motors.
    The lowest setting requires about 20W and the highest 125W. So using the lowest setting for 24 hours = 0.4kWh per day. Quite manageable for an off-grid system and worth the what it will save us in heating bills. And we probably won't have it on for 24 hours anyway.

    The models I've looked at are mostly from ze Germans, but I think that in the US and Canada in particular you'd have an even wider range to choose from because HRVs are more common in residential buildings.
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  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    #4
    Re: hrv in off grid home

    Off grid, we're powering with solar two high efficiency variable speed 19 seer 2.5 ton air conditioners and propane fired furnaces.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #5
    Re: hrv in off grid home

    It is all about loction and how much effort you put into the building if you are lucky enough to do it right. If you retrofit an existing building there are ways to be comfortable from Arizona to Canada but it will take energy from somewhere.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #6
    Re: hrv in off grid home

    Stephendv, can you tell us the PassivHaus specifications you need/want to meet. sounds German...

    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #7
    Re: hrv in off grid home
    westbranch wrote: »
    Stephendv, can you tell us the PassivHaus specifications you need/want to meet. sounds German...

    Yep, it's german :D The basic requirements are:
    • The space heating demand must not exceed 15kWh/square meter/year. Our house is planned at 210 m2, so total energy spent on heating must be less than 3150kWh/year.
    • The total air-changes per hour when under 50 Pa of pressure must not exceed 0.6.
    • The total Primary energy demand including DHW, Heating, Cooling, Auxiliary and Household Electricity must not exceed 120kWh/m2/year
    • Cooling energy demand must not exceed 15kWh/m2/year

    We're currently undergoing certification of the plans, and it hasn't been an easy process to meet these requirements. We're in Northern Spain, so a temperate climate with coldish winters (down to -5C). In the end, the design now has 35cm of cellulose in the roof and 28cm of the same in the cavity walls. 20cm XPS underneath the basement floor and around the basement walls. And triple glazing on north facing windows.

    With this, we just scrape through the certification's limits. And that's considering that we have pretty good solar gain in winter through huge south facing windows.

    An HRV with heat recovery is a must for this type of build, because the house is so airtight. But apart from the air-quality, the energy savings from heat recovery in the HRV are significant. This same house without a heat recovery HRV would need 30% more energy for heating!

    More technical details about the specification here: http://www.passiv.de/07_eng/index_e.html
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: hrv in off grid home

    Can you give us a rough idea of the R-value of your basic assemblies( floor/wall/roof) etc. 35cm of cellulose in the ceiling is what R-value for example?

    Tony
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #9
    Re: hrv in off grid home

    So as not to hijack this thread, I've answered your questions here: http://forum.solar-electric.com/showthread.php?p=41709#post41709
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