Sustainable
Pool Hall Design

I. Introduction

For indoor pool projects, the design of the pool itself is straightforward as the water circulation and disinfection systems are exactly the same for indoor and outdoor pools. The complexity of the project lies in the Pool Hall Design.

It is necessary to control the warm and humid environment, ensure that all facilities operate properly whilst being easy to maintain. And energy costs must be minimised so that it is economic to run. As a consequence Pool Halls are often extremely complex and difficult to design, especially where space is restricted.

II. Air/Water Quality and Sustainability

The sustainability of every indoor pool project depends on the Client having control of the air and water temperatures and the relative humidity. This is always provided by an Air Handling Unit (AHU).

For domestic indoor swimming pools the best AHU's combine a dehumidifying heat pump with low energy digital fan technology, enabling highly effective environmental control with minimal energy use.

The pool plant room must be at the same level as the pool hall so that the Air intake of the AHU can be placed at low level and as close to the pool as possible. The AHU must also be provided with a fresh air intake and a waste air outlet that need to be connected to the atmosphere outside - preferably through a wall with the inlet and outlet grills at least 2m apart.

It is necessary to position the plant room over part of the Undercroft that must be provided in an indoor pool - for more details see below.

The installation of supply ductwork to the diffusers that create a curtain of warm air in front of all the external glazed areas can be very costly and there may just not be enough space in the Undercroft to accommodate it.

In these circumstances, the plant room access door can be of the "sealed room" access type so that the plant room and undercroft become the plenum chamber. In these conditions, care must be taken to make sure that there are no leakage points from the plant room or the Undercroft.

III. Plant Room & Undercroft

The plant room must be as close as possible to the pool itself. It is also vital that the cables and pipework running between the pool and the plant room are accessible for maintenance and repair when leaks arise.

The best structural solution is to provide a flat slab over the entire footprint area of the pool hall and plant room so that the basement walls and pool tank walls can be built on it. The void between the basement walls and the pool tank walls is then covered with a beam and block floor slab that spans between the pool tank walls and the basement walls. This provides a structurally robust and insulated substructure. The "Undercroft" areas - as they are known - provide dry accessible space for all the ducting, pipes and cables that are completely accessible for maintenance. Part of, or the whole, of the plant room floor can be provided with an open mesh grid that facilitates the installation of the cabling and pipework.

This approach to indoor pool design is far easier to build and hence cheaper than in the past when pool halls were designed with the pool hall having conventional deep strip foundations and the pool with its own separate foundation. As a result all the ducting, pool fittings and pipework were buried in the soil between the swimming pool and the pool hall foundations. If there was a leak from any of these fittings the expensive pool hall floor would have to be dug up and the ducting is susceptible to corrosion. This always tends to happens when a pool project is built using an Architect and a Pool Installation Contractor.

Pool Plant Room

IV. Pool Hall Layout

A typical pool hall will include changing facilities, showers, sauna, lounge area, plant room, access and access routes and possibly a gym.

Lounge areas in the pool hall with chairs and a coffee table are often designed into the layout. They are never used because the atmosphere is too hot and humid to sit in unless the pool cover is on the pool and the humidity levels are set very low. A comfortable environment will then take about an hour to be achieved and will cost a lot in energy. Some layouts feature a bar with seats - this is even less likely to be used as everything in the bar is hot and wet.

Saunas are designed to provide very dry heat and will not work properly if the sauna shares the same air as the pool hall. Metal elements in the sauna will also corrode very quickly.

It is vital that the pool hall air is not shared with the rest of the house because the structural elements can be damaged and the cost of running the pool will increase significantly. Hence it is preferable if there is a transit zone between the pool hall and the house accessed by two doors with adequate draft proofing.

The cost of running the Air Handling system relies on the volume of air being treated and hence the volume of air needs to be minimised by laying out the pool so that the air in these ancillary facilities is not part of the AHU system.

Gym & Leisure Facilities

The gym can overlook the pool but must be separated without direct access because a gym needs to be dry with a temperature 7-8°C below the pool hall temperature. Furthermore if the access to the gym is from the pool hall every time the door is opened the gym will fill with warm, water laden air. As soon as the door is closed and the gym temperature drops the water vapour will condense in and on the gym equipment and ruin it in a few months.

Wheelchair Access

It is increasingly important for wheelchair users to access the pool without any support from someone else. Cranes that lift individuals from the wheelchair into the water are not easy to use and most people are understandably very nervous of them.

New equipment called "PoolPods" have become popular in commercial pools and are now available for installation in private domestic pools. They provide fully safe and quick pool access but the pool structure needs to be specially designed to incorporate their installation. Bluepools can provide the complete design and installation service for the Pool Pod.

Building Pool Halls

V. Construction Materials

Structure

Clients must be careful when they appoint a Structural Engineer. We sometimes see basement and pool structures where the structural elements are twice as thick as they need to be and where the concrete has been designed to the wrong Code of Practice all resulting in a massive waste of money.

Bluepools always uses Polyblok ICF forms for the basement, pool and pool hall walls (up to eaves level) because they are such a cost effective way of building insulated retaining walls below ground and because structural frames are not required.

Pool halls are always long, relatively narrow building and this always results in wall panels that need to be braced by frames to resist wind loading and at least two are required in every pool hall. The frames can be in structural steel (needing expensive corrosion protection) or glulam timber - both types are very costly and increase the width of the pool hall by about 500 mm to provide the space required for the frames.

The ICF formwork ensures that the June 2022 update of the Building Regulations can easily be complied with. This includes the insulation level and air leakage requirements that will be so difficult to deal with in cavity wall and timber frame construction.

Building with ICF

External Finishes

The polybloks allow virtually any external finish to be used including render, weatherboard, slip bricks or a full width brick skin.

Internal Finishes

Any internal finish can be applied to the ICF forms provided that it does not deteriorate under the damp conditions, as any form of gypsum plaster does. Render painted with exterior grade masonry paint and silica and cement based boards are all suitable and they can all be covered with tiling if required.

The roof structure could incorporate steel or timber components and should always be of the “cold roof” type so that the risk of damage from leakage of the pool hall air is reduced. The ceiling must always be provided with a vapour barrier and this is best provided by a “Stretch Ceiling” that is connected to the internal finishes in a way to stop air leakage. This protects the roof structure and minimises running costs.

Bifold Doors and Skylights

Many Clients install these at massive cost and never use them. They seem like a good idea but they are very likely to jam and become unusable because there are so few days when the weather in the UK is good enough to use them. Several sliding patio doors are a lot less costly and seem to work really well.

Furthermore after they have been open the pool hall Air Handling Unit will take a long time to get the pool hall air back to the normal conditions and this will be costly.

Lighting

All the lighting on the pool hall walls needs to be of low voltage and needs careful planning.

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