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Does hot tub need side vent for moisture?


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Hey gang - I have a cal spa hot tub up here in Canada. The base is heavily insulated. I filled the side frame with rockwool comfort batt r16. Then, I wrapped the sides in vapor barrier that I stapled. 
 

It heats up and maintains heat well. Except there’s a high amount of moisture dripping down the inside of the vapor barrier. 
 

obvious that moisture will cause a problem. So it needs to be vented somehow. My question to you folks is how do you vent a tub side? And is it common to vent a tub? 
 

My neighbors hot tub does not have vapor barrier, and therefore no vent. Because mine does, I suspect it needs to breath. Any suggestions?

my thoughts were too add a vent through the insulation and vapor barrier like this: 

Provent Exhaust Hood White 4 inch

https://www.homedepot.ca/product/dundas-jafine-provent-exhaust-hood-white-4-inch/1000502245

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1 hour ago, CanadaBeachHotTub said:

Hey gang - I have a cal spa hot tub up here in Canada. The base is heavily insulated. I filled the side frame with rockwool comfort batt r16. Then, I wrapped the sides in vapor barrier that I stapled. 
 

It heats up and maintains heat well. Except there’s a high amount of moisture dripping down the inside of the vapor barrier. 
 

obvious that moisture will cause a problem. So it needs to be vented somehow. My question to you folks is how do you vent a tub side? And is it common to vent a tub? 
 

My neighbors hot tub does not have vapor barrier, and therefore no vent. Because mine does, I suspect it needs to breath. Any suggestions?

my thoughts were too add a vent through the insulation and vapor barrier like this: 

Provent Exhaust Hood White 4 inch

https://www.homedepot.ca/product/dundas-jafine-provent-exhaust-hood-white-4-inch/1000502245

Don't see that helping much at all, it's a dryer vent and those louvers will only open when there is a force of air opening those louvers, with no forceful air from your hot tub, The louvers will never open.

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Hot Tubs need to breath. Venting is usually located near pumps to keep them from overheating. Over insulating can cause problems. A single spa pump running for 10 mins will generate 160+ degrees then add a second pump and that's a lot of heat and $$ you are spending. It is best to use that heat and $$ to your advantage. If you now have to add a vent to introduce cold Canadian air you may want to reconsider your set up. Some MFG's use vents and it is not uncommon but it confuses me. Why add all that insulation only to have to use a vent bringing in cold air. Works in the summer but not so great in Winter. Some use adjustable vents that can be closed in Winter months but customers almost never use them properly or forget to open/close them when necessary and how do you know when it's necessary. This time of year (fall) you can have temperature swings of 50 degrees in hours. Since you have already bought your insulation my suggestion would be to eliminate the vapor barrier and use heavy garbage bags then wrap and Tuc tape the rockwool. Place the bags in between the framework of the spa only and leave any uninsulated areas inside of the bagged rockwool open to allow the heat and air from the pumps to circulate within that void to work in your favor. A lot of spas will shed heat from along the top edge of the framework where it meets the acrylic. If you have the vapor barrier tucked up in there you might want to trim it down a bit to allow heat and moisture to escape. Heat rises.

Where in Canada are you located?

You can buy an adjustable vent made for spas:

 https://www.hydropoolhottubs.com/en/Shop/Products/Parts_And_Accessories/Cabinet_Pieces/Cabinet_Vents/2005094__2005094_-_Cabinet_Vent_Light_Grey in various colours to match your skirting. 

Various styles here: https://waterwayplastics.com/product/spa-accessories/

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Appreciate your replies. I will get that vent and place it near the motor. 
 

I only have insulation in the side wall frames. There isn’t any under the tub, so there’s lots of open air under there. 
 

I am in northern Ontario, so our winters can be quite harsh. Even last night with a 4kw heater, the tub can only maintain 98 degrees with the cover off. That’s mostly because it was so windy as well. 
 

Do you recommend the vent be near the bottom or the top?

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5 hours ago, CanadaBeachHotTub said:

The base is heavily insulated.

 

50 minutes ago, CanadaBeachHotTub said:

There isn’t any under the tub

 

What brand/model spa do you have?

The Hydropool pic below has 2. Bottom for cooling the pump and higher up to vent heat but all spas are different. Your issue is also different. Not sure venting will solve the moisture issue you describe. @RDspaguythoughts? 

HOT TUBS

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Canadian spa tech, I was referring to insulation in the open space under the tub. The frame itself has blue rigid insulation between 2 3/4 plywood. In the frame under the tub, there’s no batts in garbage bags. 
 

I had my friend and spa expert take a quick look and it was obvious. I have vapor barrier on both sides of the wall insulation (inside and out). So they vapor has no where to go. 
 

not sure why that didn’t occur to me before. It’s not like we put vapor barrier on the outside of our insulation in homes *face palm*
 

I also added a vent to the side near the motors through the insulation and interior vapor barrier. 
 

I think it should be fine now :)  I appreciate everyone’s response and I’ll update with progress. 
 

 

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