Any indoor hot tubs in A/C conditioned rooms?

[johnvb]

If so, what/how did you come up with the hot tub's BTU heat gain, cover on and off?

[Snowbird]

I'm not really sure what you mean by heat gain, but.... when we go on vacation we set the tub to 85 degrees. but it only drops from 99 to 95 after 10 days.  

Here in Pittsburgh, we haven't had to use the AC yet.   In fact our furnace hasn't come on for 2 months - just ceiling fans top circulate the air and the big whole-house exhaust fan when it gets stuffy.  Lately we usually keep the windows open in our tub room but in the winter they are only open when we are in the tub regardless of outside air temp.

What other info can I give you to help?

[johnvb]

Heat gain (or loss) is the term used when sizing cooling/heating equipment.

If you have a 3 ton a/c unit (1 ton = 12,000 BTUs) cooling your home, the HVAC designer should of come up with around 36,000 BTUs of  "heat gain" energy that has to be removed to maintain a certain indoor temp at a certain outdoor temp.

Sizing cooling loads for individual rooms are determined by things such as walls, floor, ceiling, and window construction/insulating factor, orientation of the walls to the sun, etc.

In an indoor hot tub room, the actual heat and humidity put out by the tub, which has to be removed from the room, would be a big additional load on the a/c unit.

I plan on consulting my hot tub maker, along with other sources to try to get an idea of what I need. Just wondering if anyone here has actually had a system properly sized and installed in their room.

(I was in the biz in a past life, but specialized in HVAC&R repair, not heat load calculations.)

[Vinny]

There is a forum, hvac_talk, I believe and there are people there who know or might know about this. There is a HVAC calculation program but when I used it, hot tubs were not in the equation.

I would imagine that a tub doesn't give off too much heat unless it's pumping (circ pump included) but the humidity is probably sky high. I also don't know if I would want that air to be mixing with the rest of the house's air because of the chemicals. I've heard about the damage a tub can do to a building because of the humidity and chems ... just something to think about.

[johnvb]

Yes, I've heard others warn about what spa chemicals can do to a cooling system, although never witnessed it myself.

Around here, the Atlantic salt air can make a 1-year-old rooftop a/c on the beach look like it's been there for a decade.

I plan on using the hot tub room as the "mixing box' for an energy recovery ventilator. The main system will blow cool supply air into the room; return air from the room will go though the ERV, then to the outside of the house. Makeup air from the outside also goes through the ERV, then into the main system's return air.  

Hopefully this will help keep the nasties out of the house. But right now we are dumping a limited amount of air into the room, which returns back into the main house (but not the A/H unit). The smell is barely noticeable right at the point of return.


http://www.toolbase.org/techinv/techDetails.aspx?technologyID=122

[Vinny]

I thought the ERV was a membrane type device where the two sets of air were in cojoined "chambers" (for lack of a better word) and the air is circulated through there.

I guess if the air doesn't get to pool water anywhere then I guess corrosion would be kept to a minimum.

[Tubaholic]

Our tub is indoors and the room has a HVAC system that is hooked up to the rest of the home. It could be cooled  but with the skylights that open and all the sliders we use it as a giant screen room in the summer. In the winter we do heat it  and also have a wood stove in there. No matter what season we can close this room off from the rest of the house when ever needed.
Enclosed is a link from an earlier post I had...enjoy
http://photobucket.com/albums/e195/Tubaholic/Hot%20Tub%20Room/

[johnvb]

That's a gorgeous room, looks like you could get a lot of use out of it. It would be a bear cool something that large around here, definitely would need a separate A/C system.

Our room has an 8 x 8 tub, in a 14 x 12 x 8 room. Just enough space for the tub, a tub exit area and mini bar set. Pretty much dedicated to hot tub use only, but the upside is it takes smaller equipment to vent and cool (the tub by itself keeps the room in the 50s-60s in the winter, which is great for tubbin').

[Snowbird]

I am not too worried about the effect of chemicals on the HVAC system.  We did not put a cold air return in the HT Room and it has a serious vent fan controlled by a humidistat set to 70% in the winter and 90% in the summer.  There is some air movement between the HT Room and the rest of the house but not so much it could hurt the HVAC system.

[Tubaholic]

Thanks Johnvb for the nice words.. We do use it all the time as the wife and I go in the tub 5+ days a week on average. It has been my favorite couch for almost 2 years now!! All I need is the remote for the TV and I am good to go... When we use it in the winter months we close it off from the rest of the house and open  a couple skylights and the temp drops like a stone... Also we have found the wood stove does a very nice job of getting rid or moisture so thats never been an issue for us. Between the stove and all the skylights/windows no exhaust fan is needed.