When installing windows, particularly windows with no visible fixed frame such as Velfac windows, it's really important to get the detailing correct. Few manufacturers seem to offer details for awkward junctions such as sill corners which can lead to poor or leaking installations.
We regularly get asked how to detail windows when installing our insulation systems so we’ve put together some key points to bare in mind when doing so.
Do bare in mind that these suggestions should be used in addition to the manufacturers recommended details and that every situation is slightly different so not all points made may apply.
One area that is sometimes overlooked whilst on site is the weather tolerance of the materials being used. The UK is well known for it’s high rainfall and for it’s ability to surprise, at any time of the year.
We believe that when building, materials should be robust enough to withstand the weather and being handled by installers.
The last thing you need on a building site is for your materials to break or become so saturated with water, they’re not fit for use.
The prospect of having at best to replace or at worst, buy some new material, is extremely inconvenient; especially if budgets and timeframes for the project are tight.
When using wood fibre insulation boards in particular, you need a high density board with good weather and impact tolerance.
Some wood fibre boards can become saturated with water and even break when sitting around on a building site. This can be due to their lack of density and use of synthetic glues that hold the fibres in the boards together.
We supply the UdiSPEED board which is designed to be highly weather tolerant and impact resistant, yet still give all of the benefits of breathability and flexibility.
It’s high density and because it doesn’t use synthetic glues to hold it together, means that it can cope with a wide range of weather conditions and high force impact. This makes it ideal for use in high traffic areas such as schools and public areas where impact is likely to occur.
Whilst we don’t recommend you let our boards get saturated, if this does happen they dry quickly and return to their original, tough state, ready to be rendered.
Can you suggest any materials for internal insulation of an old building?
For internal insulation you could use our UdiIN or UdiINRECO systems which are both wood fibre insulation board based system that are fixed to the interior of the walls to insulate. They are extremely good at managing moisture and help dry buildings out. In addition to the internal insulation you would need to look at the exterior of the walls as it becomes important to ensure that driving rain does not accumulate in the walls. We would normally recommend that the exterior is either rendered or has an impregnating, water repellent cream applied to it to ensure weather tightness.
For roofs I would suggest the UdiIN wood fibre insulation system along with the UdiFLEX wood fibre batts for insulating between the rafters. Please see our other Wall Insulation and Roof Insulation systems for more info.
How would you fix internal insulation to cob walls?
The UdiRECO wood fibre board can be fixed directly to uneven surfaces such as brick or stone with UdiASSEMBLY Masonry fixings. Where you have cob this is not possible as the material is too soft to hold the fixings. Instead it can be fixed by installing timber battens into the cob which are held in place with Helifix bars to allow simple UdiASSEMBLY Timber screw fixings to hold it in place.
Once the boards are fixed in place the UdiMULTIGRUND render system can be applied as the base coat with the Baumit Kalkin Glatt lime finishing plaster to finish it.
Our walls are cement rendered, can this cause problems with moisture and damp?
Cement renders can be a problem but only if moisture is able to get behind it. It is worth checking around window sills to see if there are cracks where rain can enter and also across the whole external facade. Cement render in itself is not actually as impervious to moisture as many people think. However, it is usually accompanied by vinyl masonry paint which is incredibly impervious to moisture and which can cause many moisture related issues.
Generally, if the render is in good order and not letting moisture in then leave it in place. If it is cracked and allowing moisture in then it would be best replaced with a vapour permeable material such as the Baumit RK39 hydraulic lime render.
Our internal insulation systems use the UdiMULTIGRUND plaster to regulate the flow of moisture into the walls from the interior. This prevents damaging levels of moisture accumulating in the walls, even if they cannot dry easily towards the exterior.
How does UdiRECO compare to Polystyrene or PIR boards?
The 80mm UdiRECO board has an overall conductivity of 0.044 W/m2K so would be equivalent to 60mm of grey EPS or around 40mm of PIR.
However, neither of the other two are able to manage moisture and I would never recommend that they be used internally. They are very likely to allow the accumulation of moisture within the wall construction which in turn is likely to allow the decay of the joist ends or lintels in your wall.
Wood fibre manages this extremely well and will, with the right wall preparation, prevent this accumulation occurring.
How does UdiRECO compare to insulating plaster?
Compared to Baumit DP85 insulating plaster, the UdiRECO system provides a faster, drier way to insulate the walls of your building.
The normal build-ups of the systems would be as follows:-
Whilst this is simpler to install as it can simply be spray applied, it will take quite a while to dry.
For the UdiRECO system I would suggest the following:-
Although the installation of the wood fibre system is slower than spray applying the insulating render, it is dry and there is no waiting time for it to dry.
However, this system does rely on reasonable stonework and will only accommodate 20mm variation in the surface. If you can point the stonework so that the variation is within this amount then the system could be viable.
One final point to make about the walls is that when you insulate them you reduce their ability to dry. This is because one side is covered and less able to dry plus you are reducing the amount of heat passing through the stonework to dry it out.
I would therefore recommend that either a render or water repellent cream are applied to the exterior to reduce any water ingress from rain.
Are their warranties/certification with UdiRECO?
As with all insulation systems, there is a manufacturers guarantee for the materials and the installer (you) would guarantee your labour/application. In terms of warranties, you can purchase a warranty from an insurance company or from the manufacturer but this is generally only of any use if you or Unger cease trading and is obviously an additional cost.
The system comes with it’s own render system which includes a lime based base coat render (with mesh) and a silicone polymer finish render (1.5mm). This is designed for use with wood fibre and is required for the manufacturer’s guarantee.
Do the UdiIN2CM boards grab the wall & adhesive immediately or is the chance to slide panels about and up to edges?
When bonding the boards to the walls they do adhere fairly quickly and there is only limited opportunity to move them when bonded to the wet adhesive. You can peel off and start again without too much issue but you can’t slide the boards around once on the wall.
Is an air gap left in the honeycomb between the solid board and adhesive?
The honeycomb layer does get partially filled but when I’ve cut through it you can see only 3-4mm is being filled so there is still 11-12mm with air inside.
Has it been used as an internal board (fixed with adhesive) upon which a thicker Udi board is screwed too in order to increase insulation thickness?
In terms of layering up the board with other boards I don’t think this would be a cost effective way to do it as it would be cheaper to apply a levelling coat render to the wall and then mechanically fixing the thicker boards as normal. Additionally, if you increase the thickness of the insulation you will then need to use the UdiMULTIGRUND product to act as a VCL.
Could it suit some rubbly walls we have where it’s difficult to get a mechanical fix?
The UdiIN2CM is great for walls which are friable and difficult to fix into but only to hold the board itself, not for adding additional layers of insulation.
In terms of condensation analysis I would have concerns regarding an air pocket between wall & wood fibre facing in the honeycomb layer. Have you performed any analysis of this?
Because of the thickness of the boards there is no condensation likely, the interface of the board and wall is well inside the dew point. The product has been tested by Dresden University with no issues.
Our walls here are slate rubble which are very difficult to fix into and a foundation layer would need to be very thick to take a fixing, take a long time to dry in typical Wales climate to become hard enough to receive a fixing for UdiRECO or UdiIN2CM. This does create a large hole in the build schedule and a lot of added render costs & internal moisture.
I see a lot of people around here using a hemp lime render instead these days which grabs the slate & lime rubble nicely and finishes well in a 2” layer and is quick and cost effective. Have you fixed a UdiRECO board over this in the past – it tends to be a bit soft for fixings?
Slate rubble is a very difficult medium to apply any insulation to because of it’s friability. Hydraulic lime renders, such as Baumit’s RK39 , will quickly fill out the surface and provide a flat enough surface to apply the board. This will then keep the amount of UdiFOUNDATION coat render to a minimum. The alternative is to spray apply an insulating render, such as the Baumit DP85 to do the same job as the hemp render does. The DP85 has lower thermal conductivity so would not need to be as thick as the hemp and has very much shorter drying times too.
With regards to the UdiRECO, you do need a surface that is fairly robust to fix it to. Unless the slate will take the fixings I would not suggest this as a solution and from memory the slate is too soft for the fixings to hold in adequately.