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Ground source heat pump, underfloor heating and screed in Bridge of  Allan

Ground source heat pump, underfloor heating and screed in Bridge of Allan

Our team of fitters have recently completed a 350m² underfloor heating and screed project in Bridge of Allan, Stirling. The property is undergoing some extensive alterations and Incognito Heat Co. have been tasked to deliver a brand-new underfloor heating system and a ground source heat pump system to heat the entire property.

Due to the scale of the property, two underfloor heating manifolds are necessary, and these have been installed at opposite ends of the building to manage unwanted heat build-up on the approach to each manifold.

To maintain the highest standards, Incognito Heat Co. manage each step of the project from floor preparation, design and installation of the underfloor heating pipework, right through to the application and levelling of the liquid floor screed.

Underfloor heating with ground source heat pump installation in Bridge of Allan, Stirling

We believe the only way to achieve a quality result is to invest in quality suppliers and installers. Our screed material of choice is Cemfloor, which is a high performing cement based liquid screed. The product is available through a select number of concrete batching plants who must adhere to the most exacting standards and is installed by our installation team who themselves undergo regular product training.

Around twenty-five cubic metres of screed was ordered for this property, to be pumped and levelled in one continuous operation. On a project of this scale, a dependable supplier is called for who can ensure that material is always available, and at the correct consistency. For this we turned to our longstanding supply partners, Grange Quarries who have constantly performed, both in terms of reliability in deliveries and the quality of material.

Upon arrival, all fresh screed is tested for the correct flow rate. This test allows our lead installer Don to judge whether the material is within tolerances, and can be used immediately, or whether further judicious additions of water are required to bring the material to the looked-for workability. Our team is trained by the manufacturers and will if necessary, reject any material that falls outside the high standards we demand. A successful flow rate test result is always a welcomed outcome on what is always a very busy day.

Material is pumped into the building, and being liquid, it encapsulates the heating pipes very well. At this point it is apparent why such care and attention has been expended on the preparation, as a successful pour will often hinge on the standard of workmanship of the team working directly before.

Following placement of the material, the screed is worked with dapple bars to finally displace any entrapped air within it. On the last pass the surface of the screed is sprayed with a curing agent which creates a ‘skin’ to prevent excessive water loss which can lead to issues with cracking.

Time-lapse video:

Before our team leaves site, we will wash down all our equipment, so it is important that space is set aside for this messy but necessary task.  All windows and doors are shut to prevent air movement across the green screed whilst it is in its infancy. Care should be taken to guard against damage from foot traffic and point loading until the screed has gained full strength.

Full instructions on the care and maintenance of the new screed are supplied to the builder, so the minimum possible time is spent getting it to a point where floor finishes can be applied.

Quick drying screed

Quick drying screed

It is a boast of ours that we are completely indifferent about the heat source that connects to our underfloor heating...well, when it is not one of our heat-pumps, that is. But apart from that if it produces hot water, you can connect it to one of our systems, however we do like to know what that heat source is before we start designing. If for example the heat source has a low flow temperature, we will design the system differently to a system that has a higher flow temperature. To date we can list conventional gas and oil boilers, electric boilers, ground and air source heat pumps, biomass boilers, hybrids and even AGA and Rayburn style range ovens among the appliances we connect with.

Renewable Energy

For our clients we can offer combined pump/blending valves (the most popular configuration for conventional heat sources), in-line blending valves and bare manifolds if the heat source has sufficient pump capacity. On this renewable energy project our client has fitted a Windhager pellet burning boiler, combined with an evacuated tube solar thermal roof mounted system.

Temperatures from this system therefore will potentially exceed what is regarded as the safe limit for floors, so it was necessary to incorporate a means of tempering the flow from the boiler. As the integral pump within the Windhager pellet boiler was powerful enough for the underfloor heating system, a three port blending valve was supplied. This takes water from the boiler into one port, another port takes water returning from the underfloor heating system (therefore cooler) and the resulting mix is fed to the underfloor circuits.

Quick drying Cemfloor underfloor heating screed

We were contracted to provide the underfloor heating and the screed over the pipes. The depth of screed is typically around 50-60mm. Traditionally a sand/cement screed will be laid to 65-75mm, this operation is quite labour intensive and the results we are sad to say, are only as good as the screeder doing the work. Among the advantages of flowing screed is the speed of application, 300m² to 500m² per day is easily achievable, an area that couldn’t be countenanced by manually applied methods. Access issues are overcome too, as we frequently find when confronted with difficult sites. With hoses extendable up to 100m there aren’t many places we can’t reach.

Fluidity checks

It was just before we started the project that we learned of a potential problem- the client was moving in within a very short timescale, the Cemfloor underfloor heating screed needed to be dried within an impossibly short time! Fortunately for all concerned, a high performance cement based screed has been developed, our project was among the first in Scotland to receive it. Its exact composition remains a trade secret for the moment, but you can expect to see more of this remarkable material in the future. The underfloor heating screed behaves exactly as we would expect a flowing product to do, but most remarkably it will be ready for tiling within half the time of any other comparable material. The product is batched at the concrete plant, ensuring strict quality control is maintained; further checks on the fluidity of the material are carried out on site prior to discharge.

It all comes together

The project was completed without hitch, the underfloor heating installation was carried out in a neat and tidy fashion (some might argue that out of sight is out of mind- but our fitters would disagree) and the underfloor heating screed was timed for the day after the UFH was finished. As the site was in a mid terrace location there was little scope to lose surplus material, a site survey was carried out to confirm the quantities required. The screed team protected the immediate vicinity against concrete splashes, and there was minimal disturbance for the neighbours. We worked closely with the installers of the bio mass system and the electricians and plumber on the project, and the client was kept informed about progress at each stage.