underfloor heating pipe being laid on Lewis Plate
Another mention in the house building press

Another mention in the house building press

Underfloor heating: your questions answered

The Lewis Deck has been picked up by a number of magazines over the years, here is the latest mention in a discussion about underfloor in the Real Homes Magazine:

Underfloor heating: your questions answered

Underfloor heating: your questions answered

Thinking of installing underfloor heating? Real Homes has posed your most-asked UFH questions to industry experts

Wet vs dry systems

As electric systems are installed directly under the floor covering, and work independently from your central heating system, they are particularly useful for one-room installations or where the sub-floor level is already set. The wire or matting systems are very thin (around 3mm) and shouldn’t cause problems with differing floor levels – thus creating little disruption to the existing room.

Wet systems circulate warm water through plastic pipes installed underneath the floor and are connected to the main central heating source. This system tends to work best when the pipes are embedded in a screed, as this helps dissipate the heat, so it is suited to new floor constructions where the sub-floor can accommodate the pipework and cement screed. Wet systems are therefore more likely to be used in new-builds and extensions or during major renovation work.

Efficiency

Wet underfloor heating (UFH) systems generate temperatures of around 40°C to 65°C, meaning that the actual floor temperature will be on average between 23°C and 32°C. This is actually lower than a standard radiator, so your household heating costs should be reduced over time.

Ease of control

Specialist UFH controls are vital to ensure comfort, responsiveness and energy efficiency. UFH takes longer to heat up and cool down compared to radiators, so to overcome this time lag, programmable controls are essential.

For households with irregular or limited occupancy and for holiday homes, it is useful to have remote control so that you can turn it on an hour or two before arriving. Remote control is also useful if you forget to turn the heating off.

Getting the right insulation

Underfloor heating will always be more efficient and cost-effective when fitted above insulation, as this reduces downward heat loss and forces heat up into the room where it is wanted. In new-build homes and extensions, floor insulation will be incorporated to meet Building Regulations, while on refurbishment projects insulation can usually be added.

Taking up existing floorboards to add insulation between the joists is fairly straightforward. Adding insulation to a concrete screed floor, however, will mean that the height of the floor is increased so skirting boards and doors will have to be adjusted accordingly. We always recommend speaking to a reputable company, as they will be able to offer advice based on the individual characteristics of your home.

Choosing flooring

Solid floors, including stone, porcelain, ceramic, terracotta and slate are ideal, as they tend to have great thermal conductivity and will provide good heat output when it comes to underfloor heating. If you prefer timber flooring, always check with your supplier to ensure it is suitable for use with underfloor heating, or consider engineered timber boards that, due to their construction, tend to be more stable during changes in temperature.’

In both cases, bear in mind that temperatures shouldn’t exceed 27°C. Most top-of-the-range laminates can also be used with underfloor heating, as can all carpets — although you may find heat output is slowed down a little, due to the combination of carpet and underlay.

Potential faults

The main cause for concern for many prospective buyers of warm water underfloor heating is what to do if the pipes leak. However, unless a nail is accidentally put through them at some stage, this simply does not happen. There are no joints in the floor and the various pipes used are designed and tested to have a 50-year life expectancy at temperatures and pressures that exceed those required by the system.

If accidental damage should occur, then individual pipes can be pressure tested to locate the correct one. In timber floors, the pipe can usually be exposed to allow for repairs, while screed floors will need to be excavated to uncover the pipe.

Choosing the right system

It’s particularly effective for large open-plan spaces – particularly those with high ceilings – as the entire floor radiates heat upwards so you benefit from warm feet and even room temperatures. This radiant heat also means reduced draughts, moisture levels and airborne allergens.

Typically underfloor heating is more than enough as a stand-alone form of heating. However, its capabilities will often be dictated by other factors, such as floor coverings and a building’s insulation levels (especially walls and windows). This is why heat-loss calculations are so fundamental, as having looked at a building’s individual thermal performance they will tell you how much heat you need to generate.

For example, a poorly insulated room with lots of glazing may not heat fully when it is cold outside (which means additional insulation or supplementary heating may be necessary). Floor coverings also play an important role. Normally, stone and tiles are excellent options, as are carpets with suitable tog ratings. If you’re keen on timber, however, remember it has a lower temperature tolerance.

Underfloor heating vs radiators

Where cost is an issue, the expense of installing underfloor heating may outweigh the advantages, especially if it involves removing concrete floors and re-screeding. In houses not occupied during the day, underfloor heating’s slow warm-up and cooling time (which can be up to four to six hours) may not suit you.

‘A combination of both systems can often be the best answer for many homes, as radiators can be easily incorporated into an underfloor system. A good compromise is to install underfloor heating on the ground floor, with radiators upstairs to accommodate the different requirements for living and sleeping spaces, especially as many people still want heated towel rails in their bathrooms.’

 

FAQs

Ask CDI a Question

  • Q

    Do I keep my joist centres at 400mm when using Lewis Deck?

    A

    One of the great things about using Lewis Deck is that it opens up a number of different options for you and one of them is around joist centres you can work with.

    Traditionally we see the vast majority of architects and designers insisting that timber joists be installed at either 400mm or at most 600mm because this is the limit of what timber floor systems will effectively span to. Now with Lewis, because of its unique profile (with the dovetails dimensions) and the way it interacts with the thin (50mm) screed laid on it, you can actually go much wider than these figures. With a 50mm screed, on top of the sheets, Lewis allows you to have unpropped centres of up to 1200mm (1.2m). Even at these much wider centres Lewis will allow you to have a permissible load of 14.8kN/m2, which in English is just under 1.5 Tonnes per m2. Now this might sound fantastic, and it is, but in reality for 95% of new build homes this figure won't really make too much difference to what you were planning on doing with upstairs. What it does mean though is that at your normal centres, of approximately 600mm, your floor becomes so much stronger than traditional forms of floor structure that it allows you to do things on the 1st floor that you take for granted on the ground floor. First of all is the obvious one, you get a solid floor, meaning no more squeaky floor boards or hearing people walking around upstairs and knowing exactly where they are up there! Having the solid floor gives you the chance to have a very efficient underfloor heating system (see our applications section for more details) which in most cases will probably mean a slight reduction in your fuel bills. Other big benefits of having a stronger floor upstairs include being able to have either thinner tiles or much heavier tiles than you can use on timber floor systems. The screed and Lewis working together pretty much stops any deflection in the floor meaning that these types of tiles won't crack or move and lift over time as the floor doesn't move or deflect! So in conclusion yes you can have much wider joist centres than the 400mm centres that you normally see on new developments but even if you wanted to keep them the same by using Lewis Deck it opens up so many benefits that you just aren't able to incorporate with traditional timber floor systems.

    Q

    Do you fix Lewis Deck down to the joists?

    A

    The short answer to this is no Lewis Deck doesn't have to be fixed down.

    Generally the reason why people choose to use Lewis Deck over more traditional floor systems is that they are looking to enhance the upper floor that they are working on. So if you are going to be looking at using Lewis then you might as well look to incorporate its full range of benefits. One of which is the major uplift in acoustic performance that you get from using the system. Getting the best results, acoustically, is achieved by laying the floor as a floating floor. This then creates separation between the supporting floor joists and and the steel deck. To enhance this further introduce a resilient strip on top of the joist. See below. [caption id="attachment_559" align="alignnone" width="300"]Lewis Metal Dovetailed Sheeting Deck with acoustic Sylomer resilient strips Lewis Metal Dovetailed Sheeting Deck with acoustic Sylomer resilient strips[/caption] When it comes to determining which of our acoustic resilient strips to use (because we have a few of them and they all do different jobs depending on the use of them and the type of structure below) we are happy to help you come up with the correct option that suits your project the best. A standard Lewis Deck floor detail (such as the detail above) easily achieves UK requirements for acoustic (as well as fire) resistance for residential separating floors. Higher performance standards are easily achievable too. Because of this we have seen Lewis Deck used frequently in in bespoke projects such as live music/ theatre venues, cinemas, recording studios, specialist test labs, plant room floors and many other commercial applications. Also as well improving improving the noise reduction between floors by not having to fix the sheets down you are massively speeding up the installation process!! Having to spend less time on site could have a positive knock on effect on the cost of your project. Please feel free to give us a call and discuss this further should you wish to do so.

    Q

    Lacomet – How come it has no scrap value?

    A

    Lacomet – How come it has no scrap value? Many of the projects that we get involved in starts with a phone call or email to us from someone researching replacing stolen leadwork. Many of these are old buildings, such as schools or churches, where this isn’t the first time that the lead has been stolen and they call us fed up with having to replace it again full in the knowledge that they will more than likely go through the same problem once more in the near future if they continue to use lead. One of the big benefits that Lacomet FL brings to a project is the fact that it has no scrap value and therefore the chances of it being stolen are massively reduced. Due to the 2 thin aluminium layers, and its five layer total construction, it is of no value to thieves. Lacomet can be recycled but the polyester based coating would need to be de-laminated first and the amount of recovered aluminum is then very low, in fact it would be easier and more profitable to collect empty drinks cans than to mess about stripping Lacomet down. We can also supply stickers that can be placed in strategic locations informing people that what is now on the roof is not lead and that it has no scrap value.

  • Q

    Do you fix Lewis Deck down to the joists?

    A

    The short answer to this is no Lewis Deck doesn't have to be fixed down.

    Generally the reason why people choose to use Lewis Deck over more traditional floor systems is that they are looking to enhance the upper floor that they are working on. So if you are going to be looking at using Lewis then you might as well look to incorporate its full range of benefits. One of which is the major uplift in acoustic performance that you get from using the system. Getting the best results, acoustically, is achieved by laying the floor as a floating floor. This then creates separation between the supporting floor joists and and the steel deck. To enhance this further introduce a resilient strip on top of the joist. See below. [caption id="attachment_559" align="alignnone" width="300"]Lewis Metal Dovetailed Sheeting Deck with acoustic Sylomer resilient strips Lewis Metal Dovetailed Sheeting Deck with acoustic Sylomer resilient strips[/caption] When it comes to determining which of our acoustic resilient strips to use (because we have a few of them and they all do different jobs depending on the use of them and the type of structure below) we are happy to help you come up with the correct option that suits your project the best. A standard Lewis Deck floor detail (such as the detail above) easily achieves UK requirements for acoustic (as well as fire) resistance for residential separating floors. Higher performance standards are easily achievable too. Because of this we have seen Lewis Deck used frequently in in bespoke projects such as live music/ theatre venues, cinemas, recording studios, specialist test labs, plant room floors and many other commercial applications. Also as well improving improving the noise reduction between floors by not having to fix the sheets down you are massively speeding up the installation process!! Having to spend less time on site could have a positive knock on effect on the cost of your project. Please feel free to give us a call and discuss this further should you wish to do so.

    Q

    Lacomet – How come it has no scrap value?

    A

    Lacomet – How come it has no scrap value? Many of the projects that we get involved in starts with a phone call or email to us from someone researching replacing stolen leadwork. Many of these are old buildings, such as schools or churches, where this isn’t the first time that the lead has been stolen and they call us fed up with having to replace it again full in the knowledge that they will more than likely go through the same problem once more in the near future if they continue to use lead. One of the big benefits that Lacomet FL brings to a project is the fact that it has no scrap value and therefore the chances of it being stolen are massively reduced. Due to the 2 thin aluminium layers, and its five layer total construction, it is of no value to thieves. Lacomet can be recycled but the polyester based coating would need to be de-laminated first and the amount of recovered aluminum is then very low, in fact it would be easier and more profitable to collect empty drinks cans than to mess about stripping Lacomet down. We can also supply stickers that can be placed in strategic locations informing people that what is now on the roof is not lead and that it has no scrap value.

Ask CDI a Question

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