Small Indoor Swimming Pool heating, Dehumidification and ventilation

Hello there,

I'm a new member, just joined today on the recommendation of a newly-met friend.

Is there anyone out there who can help me unravel the confusion that I have been placed in by various manufacturers, designers and so-called specialists, concerning a system of space heating, ventilation and dehumidification for a small indoor swimming pool that I am having installed at my house in the Gironde, inside a converted hangar with a linkway corridor to an outside door of the house.

Please don't suggest I ask my pool installer/building contractor, because he confuses me as much as anyone.

I append below in blue the enquiry/specification that I have been sending to various suppliers in the UK and elsewhere (e.g. Denmark), in the hopes of obtaining a satisfactory proposal and quotation. (I have sent a similar document but in French, to the few specialist companies I have been able to locate over here).

I would be extremely grateful to anyone who can offer advice and/or sensible suggestions.

Thank you.

Melvyn Anthony

"I wish to install a HRV heating, dehumidifying and ventilating system for the indoor pool at my house in France, to enable all-year round use. If this is something you can supply only (we have our own installers), then relevant information is as follows:

The pool is 8m long x 3.5m wide and 1m40 deep, so has a surface area of 28m2 and a volume of 40m3. It is housed in a room that is being converted from a barn and connected to the main house by a short corridor. Building construction will comply with current required U values. The pool "hall" is 13m long x 5.5m wide x 3m high (71.5m2 and 225m3). There is a large void between the insulated ceiling and the tiled and felted roof which can contain fans, machines, ducting, etc. At one end there is a small pool equipment room which should have sufficient space for more machinery, and also there is a small shower room with wc and washbasin.

It will not be possible to install underfloor pipes or underfloor ducting.

Wall openings contain a set of full-glazed upvc patio doors, a hinged half-glazed upvc door, and 3 upvc windows. There is also a half-glazed upvc door into the connecting corridor and another into the equipment room and shower room area.

The roof void must be well-ventilated. The pool can be heated as part of the overall system or we can install a separate air to air heatpump for this.

The link corridor can be heated/ventilated as part of the system, or we can heat it separately via a radiator off the main house central heating. What is important is that moist air be kept out of the corridor, presumably by maintaining an appropriate air-pressure differential between the corridor and the pool "hall".

System requirements will be:

Pool water temperature - 28 degrees C (even when down to -10 degrees C exterior)
Pool "hall" air temperature - 30 degrees C (even when down to -10 degrees C exterior)
Pool "hall" humidity - 50 to 60 percent
Ventilation needs (based on moisture evaporation given the above temperatures, plus natural ventilation of 0.25ACH) - 7.5m3/minute (450m3/hour)and an 800m3 air volume inflow has been suggested.

I do hope that you can propose and supply a suitable system at reasonable material costs.

If additional heat in addition to that which is recovered is required to achieve the desired air temperature, then this can be provided by a second air to air heatpump (or a larger heatpump can be used to heat the pool water and supplement the heat-recovery as needed). A reversible facility to cool the air in summer could be nice."


The only way you will achieve a proper and guaranteed job is to go to a specialist firm, here in France, who hold the proper qualifications and an insurance backed 10 year guarantee. You need a specialist in "Genie Climatique", in the Gironde someone such as Puel Your specification is of considerable complexity, and won't come cheap, and will in the first instance rely on a rock solid thermal study of the building(s) and the pool concerned. If you have not already constructed the pool then the design of this should be included in the study because you will need to build it with extremely efficient insulation built into the floor slab, the walls AND with insulated flow and return pipework. In my opinion any other approach will lead to an expensive dissapointment or disaster, and with little or no recourse. You should also ensure that the proffered 'garantie decennale' is valid at the time of planning and building, and does cover all the works to be carried out, including the preliminary study. Just having a "garantie decennale" is not enough.

I feel I have to add that maintaining a building of that volume to those temperatures and the pool at 28C, both with an outside temperature of -10C, you will be grateful you have four nuclear poweplants near you! Global warming...Good luck.

Hello Tim,

Sorry this is such a belated reply, but I am pleased to inform you that after much study and research I managed to put together a package that does the job I required. I purchased from one company( who gave me excellent service) an air-to-air heat-recovery ventilation system made from non-corroding materials, and from another company I purchased a pair of Mitsubishi heat pump units with interior wall-mounted emitter units for heating the pool building. From that latter company I also purchased a swimming pool air-to-water heat pump which provides the required water heating. I then found an engineer familiar with all of this type of equipment who, with a colleague, installed it all for me. I had to do it this way as I could not find one company to supply and install everything required; some even offered me equipment which was not corrosion resistant and therefore not suitable for a pool environment.

The performance of the system has been no less than I had hoped for, and I am delighted with it.

I waited to get back to you because I wanted to use the system for a couple of years, to test its integrity and running costs. The equipment and installation were not cheap, but the price was affordable. The running costs have been quite high, about double my previous electricity bill, but again, affordable.

A happy new year,

Mel Anthony

That’s good to hear Mel, You asked a tall order but glad you got it sorted. Not at all surprised you didn’t get that much help, despite the number of pools in France the knowledge is woeful.