Cold Weather Operation
Preparing for winter
Q: I live in a cold climate and I do wish to keep using the hot tub during winter. What measures can I take to reduce the heating bill in the winter?
A: The main measures involve insulation and avoiding injection of cold air. As far as insulation is concerned, the tub has four surfaces (top, floor, staves and piping) that you can fully or partially insulate. Every additional sq inch that you insulate will save you some money. Here is how.
1) The top surface is covered with a thick cover which has very good thermal insulation. You can?t do much more here.
2) The floor surface should be permanently insulated with 1.5? or 2? blue Styrofoam as shown below. This can be ordered at time of purchase if you do not wish to do it yourself.
Figure 1 - Insulated Floor
3)The wall (stave) surfaces, which makes up the largest area of heat loss, can be insulated using specially cut Styrofoam strips that are cut at an angle to match the staves and have dados so the bands won?t interfere.
Figure 2 - Styrofoam Stave Insulation Strip
3)These can be ordered from Northern Lights. Please specify what height you have available for insulation and the size tub you have. The cost will be $3.00/stave + shipping and handling. You can also make them yourself. Here are brief instructions:
Use 4x8ft sheets of 1.5? or 2? thick blue Styrofoam. First cut 3/16? deep grooves matching the hot tub band width and separation into one side of the Styrofoam sheets. Then cut the sheets of Styrofoam into strips matching the total number of staves. For example, for a regular tub you need 43 strips. The blade needs to be set an angle determined as follows: 360/2xN (Here N represents the number of staves). For a regular Northern Lights tub the angle thus is 360/2x43 =4.2°. The inside width of these strips is made the same as the repeating distance between staves which you can measure. This should be slightly more than 4-5/8inches. Cut each strip to suitable length and surround the tub with these strips. Apply two dabs of silicone caulking to keep them from falling off. Then use fabric straps with ratchet tighteners to hold the insulation in place.
Figure 3 - Insulating Tub Walls with Strips of Blue Styrofoam
Where accessories and plumbing components do not allow a contiguous strip to be used cut them into suitable pieces. It is not necessary to have every bit of the wall covered, but the more sq ft you can get covered the greater the energy saving. For built-in tubs you can apply this technique permanently, to all surfaces hidden by the deck. For stand-alone tubs you would avoid using the silicone dabs and instead have helpers hold the strips in place while you adjust the fabric straps. This allows you to remove the insulation after the winter season has past.
4) The plumbing hosing and piping is another heat loss area. Purchase suitable diameter foam pipe insulation from a Plumbing & Heating Supply Retailer or Wholesaler and surround all pipes and fittings where this is easily done.
Figure 4 - Foam Pipe Insulation Surrounding 1-1/2" Hose
5) Other considerations.
If you have a blower and will operate the tub in the winter, you should trace heat around the pipe coming from the wall fitting to the anti-siphon loop. We recommend using the optional heat exchanger blanket along with extra length 3/8” hose to achieve the trace heating. You must then insulate this leg. Unplug the blower in the winter, since you don’t want cold air blowing into the water, which will quickly lower its temperature.
Wrap blanket type insulation around both flex hoses, which join the jets, in such a manner that the top air hose will get heated by the lower water hose by convection. Otherwise the air hose may freeze because water is stagnant in this hose. It is not recommended that you do not open the jet air valves in the winter, if you want to reduce your energy bill.
We optionally supply a valve for the ozonator. While this valve should never be closed when the ozonator is plugged in, throttling the flow down will reduce the amount of cold air injected via the ozonator.