The Tender Analysis
When you receive Subcontract tender documents, invariably they’ve got differences and it’s important to make sure you’re comparing Apples with Apples.
Look out for these important cross-checks to make sure you’re comparing like-for-like proposals.
There is a number of different control systems with UFH – if there is no specification the tenderer may not include controls, or their own controls – in this case there could be three different tiers of controls which can vary the price significantly.
HIU’s are becoming commonplace so it’s important to know the specification. Some have integral pumping and temperature blending capability, and some do not. This will have a significant price impact.
Make sure you know what design is included, if it has been included at all. Heat-loss calculations are often not included, and the design should include the floor finishes being used within each room.
Some contractors insist on a minimum quantity per visit – it is important that each contractor has priced the same guidelines – i.e. there is consistency between number of units / meterage available per visit.
Some will include this – some will say it’s the plumber’s issue. Ensure it’s included as a separate return visit, and as with the install, there is consistency between number of units / meterage available per visit.
6. Screed Type
The primary concern should be that the same type of screed has been allowed for and thereafter, has it been allowed for in all areas or has it just been included for in the heated areas.
This section identifies six simple, intelligent solutions to Value Engineer a Underfloor Heating package…
1. Thermal Insulation at Intermediate Floors
Intermediate Floors do not need to achieve a U-Value because they count as party floors. Despite this, in many cases, Architects will specify the use of Polyurethane rigid foam (or PUR Insulation for short) as a high-performance insulating material. Please note you need to comply with BS-EN:1264.4, some insulation is required below UFH but typically much less than ground facing floors.
With some design calculations on the U-Values of the building, more often than not, this high-performance (and high-cost) insulation can be calculated/designed out and replaced with more economical Expanded Polystyrene (EPS) insulation that still meets the performance requirements.
2. Thermal Insulation at Lower/Ground Floors
On the lower floors where you have a block and beam floor, the Design team will often have included for a single layer (often 100mm) of high performing PUR insulation.
An alternative is to use two layers (2x 100mm) of lower U-Value Insulation such as Expanded Polystyrene insulation (EPS). Two layers of this insulation are equivalent in terms of performance of 100mm of the superior PUR insulation however far more economical.
On larger Apartment blocks party floors with acoustic requirements are often over-specified and a day or two of focus with an Acoustic Engineer, can highlight the over specification in Acoustic Insulation.
Invest a day to put together an Acoustic Report showing performance levels of the specification are met with a reduced thickness insulation and submit this together with our design for approval to take the saving in reduced material purchase.
Programming the Site Works
Underfloor Heating is a package of works that fall on the critical path of the project and just before Practical Completion.
Despite this, it is sometimes seen as a minor package of works and therefore, little attention is paid to them. Don’t make this mistake and follow these six tips for a snag free handover.
Always provide the UFH contractor with the most up to date information to minimise the volume of drawing revisions. From the outset, provide the following to enable an economical design process:
- SAP calcs
- Manifold positions (allowing enough space)
- U- values for walls, roof, windows and other fabric materials
- Details of Floor finishes and layouts marked with kitchen units and other fixed furniture – areas which need not be heated.
- Elevation and section drawings which indicate the ceiling heights and glazing so heat losses can be calculated.
Make sure timescales are understood to ensure everything is complete ahead of time. UFH is lead-time sensitive and therefore, make sure the programme includes call-off time and this is agreed with the contractor up-front.
3. Design Approval
Once design is complete, the client, consultant and other interfacing trades should review for approval to mitigate the risk of costly penetrations through UFH pipework while also ensuring appropriate zoning, adequate heating control and provision for manifold housing.
4. Co-ordination and Programming
Communication between all trades is vital for expectation setting. UFH is laid in large areas at a time, so it is important that these areas are ready. Obtain a checklist from the UFH contractor to understand what is required – as a minimum the floor area must be clear and areas such as fixed furniture and kitchen cabinets identified.
5. Working Partnership
Consider using the same UFH contractor on multiple projects – this way you can adopt consistent systems of working that maximise efficiency.
6. Check and Balance UFH
Allow ample time to get the UFH checked and balanced once all finishes are installed. This enables snags, faults or changes to be highlighted and rectified before Practical Completion. Full technical support in the way of an operation and maintenance manual should be requested at this point too.
This content was created in Collaboration with WMS Underfloor Heating, the leading Specialist in Underfloor Heating.
WMS are a leading supplier and installer of underfloor heating and cooling systems for new build and refurbishment developments in the UK.