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Tiny House Central Texas Ventilation Question

TechnoViking | Posted in Energy Efficiency and Durability on

I am in the process of building a 14×20 (280sqft.) tiny house. It has closed cell foam insulation under the floof, in the walls and in the ceiling. It’s a fairly airtight build. I am at the design stage for the ventilation system. I am located in Central Texas, climate zone 2 with long, very hot/humid summers and short, mild winters (occianaly there is a snowpocalypse). I will be using an LG 7,000 BTU mini-split that will be running continuously. I will also be using a stand alone Frigidaire dehumidifier. The kitchen is on one side of the house and the bathroom on the opposite. The mini-split and dehumidifier will be located on the kitchen side. The house is an open design with only the bathroom walled off and the sleeping loft above the bathroom. SInce I’m only dealing with 280sqft. I really want an as-small-as-possible ductless system. I have been considering the Lunos e2 ductless HRV system. However, the Lunos e2 is an HRV and in the hot/humid climate I am in, I would much rather use an ERV. Is there a ductless (hopefully wall mounted) ERV system that is available to buy in the USA easily? I can find only 2 systems that have what I want (the Fresh-R In-the-Wall and the Holtop PM2.5) but both these are not readily available in the USA. Are there any other companies available in the USA that have ductless ERV systems? Does anyone have any recommendations? Please keep in mind, I’m  looking for a true ERV, not HRV system. I see plenty of ductless HRV systems like the Lunos e2. As for the location of the ERV, I would like to mount it close to the mini-split, is this correct? One more question, I also plan to install one exhaust fan in the kitchen and one in the bathroom. With an ERV in use, should I use continuously running exhaust fans in the kitchen and bathroom or just switch them on when cooking or using the bathroom? Thanks for any and all help! 🙂  

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Replies

    1. TechnoViking | | #2

      Thanks a bunch for your help. The Panasonic 04ve1 looks just about perfect. I'm thinking instal the 04evi next to the mini split and have the dehumidifier right underneath both. Does that sound like a good set up? Also, what would you recommend in terms of kitchen and bathroom fans with a setup like this in a 280 sqft, tiny house? Continuous fans or operate them only when kitchen or bathroom is in use. Mind you, the mini-split, ERV and dehumidifier will practically be in the kitchen area.

  1. Steve Knapp CZ 3A Georgia | | #3

    Does the LG mini split include a dry mode? If so, it might provide enough dehumidification even during the shoulder seasons. I would install the ERV as far from the kitchen and bath as possible. This unit does not like to be exposed to shower steam, for example.

    If it were my house, I would install a couple of humidity sensors and monitor the indoor conditions. (One like this https://www.amazon.com/gp/product/B01AEQ9X9I/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 or https://www.amazon.com/Govee-Thermometer-Hygrometer-Bluetooth-Temperature/dp/B07R586J37/ref=sr_1_1_sspa.) You may not need the dehumidifier or to run a continuous fan.)

    Maybe one of the experts will chime in on this topic as well.

    1. Cldlhd | | #5

      My Mitsubishi mini splits have a dry mode but the problem is even though they claim to not really lower the temperature. If I leave them running that mode it'll get down to the low 60s in the house. My bedrooms each have their own wall unit and with close cell spray foam in the walls the load is too little for the wall units. Two of the bedrooms have 9,000 BTUs and one has 6,000. The problem I've run into is in cooling mode on a humid day in the summer. The temperature will quickly be satisfied, but the blower wheel continuously runs. So with the condenser/ compressor off outside, it blows a ton of humidity back into the room off of the indoor coil. I imagine having a standalone dehumidifier will help a lot in that regard. My work around was to put some Cielo breezes in and set them up with comfy temp. That way when the desire temperature is reached, it shuts the entire unit off. That's a multi-split setup, I also have a mini split with its own outside unit to take care of the living room, kitchen in general living area. Apparently the load is enough on that one and being a one-to-one unit It's capable of throttling down to a lower BTU with the inverter compared to the multi-splits and I don't have the humidity issue. In the winter just let the fan run continuously. My weather is a little different though as I'm in the suburbs of Philadelphia.

  2. James Howison | | #4

    btw, I think that 7,000 BTU sounds very high for loads, I ran coolcalc on a 16x12 building in CZ2 and loads were more like 2,000 (but it didn't have many windows).

    I am a little leary of the ductless minisplit filter in a kitchen environment, get some grease on the blower wheel and all the dust will stick (and the filters aren't great).

    After you have the dehu, minisplit, an ERV, and (multiple) ventilation fans perhaps looking at the "magic boxes" like the Minotair and the CERV2?

    https://buildequinox.com/thesystem/

    https://www.greenbuildingadvisor.com/article/energy-smart-hvac

    Heating performance looks sufficient (if I'm right on the loads), dehumification and ventilation is fine, cooling would depend on knowing the actual loads. I think the Minotair has more cooling built in.

    Can be combined with a small ducted system:

    https://buildequinox.com/news/?id=6669

    Please let us know what you decide.

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