Should I Use Board In My New Build Or Blown Bonded Bead?

In 2014, the Northern Ireland new build market constructed in the region of 6,000 homes,17% of which were timber frame dwellings, leaving around 5,000 homes built in a conventional manner, with about 30% of these being one-off new builds, largely built in rural areas.In terms of the important issue of insulation, these one-off homes tend to use larger cavity widths with 150mm being the minimum and 200mmm being common place.

Should I use board in my new
build or blown bonded bead?

This is the question often asked by architects and historically, it has always resulted in board being installed.In a 100mm cavity, architects specify predominantly a partial fill board, this being a 60mm polyisocyanurate – or PIR board as it is generally known – leaving a 40mm residual void cavity, which will meet building control regulations on TGD part F of λ0.28.However, it is a little known fact is that the blown cavity graphite bonded bead system gives the same λ value at 100mm on a full fill cavity – and guarantees that the cavity is completely filled, leaving no voids.

This can be clearly seen if you look at the video on the Energystore website www.energystoreltd.com or follow the link at
https://youtu.be/qc3dMVQ0RSc
As can be seen in these videos,bead will fill every part of the cavity,but with board, this is left to the bricklayer to install, and to ensure that the board is tight against the bottom of window sills, around vents and into corners. The manufacturers do make riser pieces and corner joints but these are rarely used.

With one-off houses, there is the opportunity to use a full fill board in the 150mm cavity giving excellent U values – but at a huge cost.If a 150mm cavity is drawn by the architect, there are three options:
1. Using a 110 mm PIR board leaving a residual void cavity of 40mm, we will see the same difficulties arising with adequacy of fill. In this scenario, the λ value on board-versus-bead,the bead will give a better U value at 0.194 W/m2k compared to 0.2 W/m2k for board. (This can be seen in the comparison chart later in this article).
2. Full fill PIR board – this is the Rolls Royce of materials, and in a 150mm cavity, it can bring values down to 0.13 W/m2k at a cost.
3. Full fill bonded graphite bead -this product, as noted above,will guarantee a full filled cavity and will deliver a u value of 0.194 W/m2k, no wastage,no storage, no build in costs,and no hassle for the bricklayer.

So the question that we ask
ourselves is why.

Is it cost? No, blown bead is a very cost effective method of insulating your home.Is it quality of install? All installers on the Energystore agrement certificate are fully trained under the system design and are constantly audited by the team at Energystore and by the regulating body the BBA (British Board of Agrement), with each installer being audited a minimum of four times per year by BBA.

With board several problems arise and this was highlighted at a meeting at the Ramada Hotel in March this year, where a CPD conference was held in conjunction with RSUA, (Royal Society of Ulster Architects),Energystore and SERC.Around thirty architects attended and SERC Lecturer John Ross presented on the issue of“Insulation Past & Present”.What emerged from this meeting was a great concern about the occurrence of thermal looping -that if board is not fitted correctly thermal looping can occur,because as little as a 1mm gap between the inner leaf and the insulation board can severely reduce the insulation qualities of the board.“Air and wind tightness are decisive factors in efficient thermal insulation.Leakage: warm air pours out uncontrolled and is replaced by cold air from outside. Research has shown that, even in well-insulated houses, around 60% of the total heat lost is due to leakage and thermal bridges. Leakage in the shell of a building is a direct cause of structural damage due to condensate,diminished sound insulation, dry air,cold floors on the ground floor.At the Institute for Building Physics in Stuttgart a test has been carried out to show the extent to which the insulation efficiency of a building element is affected by leakage: a typical construction element measuring 1m x 1m x 14cm as used in prefabricated buildings has a U-value of 0.3 W/m2K when completely tight. If there is a continuous gap only 1mm wide, the U-value is reduced to 1.44 W/m2K.This allows for a moisture stream to develop.”

The quality of install will often leave a lot to be desired.

The price of the board product is more expensive, and it will also incur additional install costs. If you ask the question on install costs you will get a multitude of answers,ranging from £1.00 per m2 to adding 2-3 man days to the build, We have assumed the lesser at £1.00. The more expensive full fill board has many hidden extras, in that it requires special corner joints and riser pieces. On top of this a vertical DPC will be required from top to bottom on all corners.Another issue to consider with the board product is storage on site and wastage, which we have not taken into our calculations.Energystore are working hard to educate on the benefits of bead verses board and we believe that in many instances it is lack of education on the benefits and performance of the bonded bead systems.

Retro fit partial fill

In existing homes which have had board fitted, we have a BBA agrement certificate to top up the residual void cavity. Homes that had partial fill board fitted can now be topped up with bead. This can cure a lot of mould issues as we find that in many instances, there are gaps around windows -particularly below sills – and mould appears on the inside due to the cold spots where the board has been left out or the corners have been knocked off. This is a very in expensive fix and can radically reduce the heat loss in the home.

Cavity extraction

Energystore, in association with SERC and the University of Ulster,have been studying the effects of wet or poorly fitted fibre in the cavity.In the last 12 months we have extracted poorly performing insulation from 350 homes.According to the result of the study by the UUJ this can increase the thermal performance of the home by up to 39%.Followed is an extract from conclusion of the UUJ report“Investigating the performance and quality of cavity wall insulation in domestic dwellings in Northern Ireland”“6.0 Conclusions The in-situ U-value measurement study demonstrated the problems associated with the variability in thermal performance of fibre insulated cavity walls. This would validate findings in the literature which suggest similar issues.The reasons for this variability can be wide ranging from poor fill techniques to fibre degradation.When the fibre was extracted and replaced with bonded bead insulation the variability decreased significantly.In addition the improvement in thermal performance due to the installation of the bonded bead was in the range 21% to 39% depending on the sensor location.The quantitative findings have been backed up by a qualitative analysis from the house residents who noticed a step change in the temperature and thermal comfort conditions in the house.”Energystore’s findings are that if the defective insulation is removed and replaced with bonded bead it will make the house substantially easier to heat and retain heat and in the case where mould has been present it will largely eradicate this.The thermal image (upper right)shows the front of one property before these improvements, while the second image (below right)clearly shows the effectiveness of these measures.

For further information, contact
Energystore Ltd on (tel) 028 90301 500, email them at
info@energystoreltd.com or visit
www.energystoreltd.com