Insulating Older Buildings

Natural Hydraulic Lime Insulating Render
Our Natural Hydraulic Lime Insulating Renders / Plasters are manufactured from top quality NHL2 Natural Hydraulic lime, toughened light weight aggregate and fibres.  Both can be applied internally or externally. The three Insulating Renders / Plasters supplied by Womersley’s are:

• Cornerstone Insulating Render
• Lime Green’s Ultra Insulating Plaster
• Anglian Lime Thermalime Plaster

Designed to improve thermal comfort, reduce heat loss and reduce condensation.  They are light weight insulating basecoats for rendering and plastering.  The Cornerstone and Ultra renders contain specialist light weight aggregates and the Thermalime contains chalk.  Each maintain their structural integrity when applied and will not crush, and provide an excellent insulation layer:

• Highly breathable
• Energy Saving – a 50mm application will reduce heat loss by up to 60%
• Improve Thermal comfort
• Builds out in thick layers at up to 20mm per pass
• Natural dehumidifier
• Suitable for direct application to most surfaces

These insulating renders / plasters are the most popular on the market due to their ease of use.  The Cornerstone and Ultra renders can be finished with Lime Green Natural Finish (External), Lime Green Solo (Internal) or Womersley’s Fine Stuff (Internal).  The Thermalime will achieve a smooth finish using a stainless steel trowel but can be finished with Womersley’s fine stuff internally, and if used externally it should be painted with a breathable paint.

 A hydraulic lime stipple / slurry coat should be applied first to smooth/ engineering bricks.
 
 

Wood Fibre boards
We have tried different Wood Fibre boards over the years and found that the best product on the market is the Lime Green Warmshell system, for internal or external application. Warmshell is particularly well-suited to older hard to heat homes, irrespective of whether they are brick, masonry or timber frame. 

• Highly breathable
• Energy Saving
• Significantly limit heat loss
• Tongue and Groove boards
• Natural and sustainable

Installing Warmshell to your home is surprisingly straightforward. It is well within the reach of a capable DIYer, and should be second nature to most builders.

All you need to do is follow these simple steps:

1. Scour the wall with a coat of Lime Green Duro lime base coat to ensure a level surface

2. Cut the Warmshell boards to size and aim to cover as much of the wall surface as possible

3. Secure the Warmshell boards to the wall surface using suitable fixings and / or Warmshell adhesive

4. Render/Plaster over the Warmshell insulation boards with two-passes of Lime Green Natural Finish (external) with the use of Alkali resistant mesh between coats OR Lime Green Solo Plaster (Internal) with the use of Alkali resistant mesh between coats

Coarse Stuff with Hemp

Uses mature lime putty blended with selected aggregates, for internal application. Like all non-hydraulic lime products, it is extremely flexible and breathable which makes it suitable for use in the restoration of old 'solid wall' construction buildings and is ideal as a 'wattle and daub' replacement in timber-framed buildings.

The addition of hemp fibres not only improves the strength and flexibility of the product, but it also increases the thermal properties of the plaster and so adding some insulation to your wall.  Please be careful as some suppliers advertise this product as Hemp Insulating Plaster which is not quite correct as the insulation values achieved are minimal in comparison to all the other products in this guide.

Hemp Lime Plaster is available in two grades - medium and fine and is manufactured ready to use in bulk bags, and tubs.

Insulating Hemp plaster

Manufactured from Calbux 90 Quicklime, Hemp and selected aggregates and supplied with a roman cement admix. For internal application. Womersleys are the only manufacturers in England of traditional insulating hemp plaster using Quick Lime. The Insulating hemp plaster is supplied with a natural roman cement called Prompt allowing for a thicker application of the plaster whilst still curing at depth. The use of a Quick Lime also acts as a steriliser for the Hemp to prevent any unpleasant smells and makes for a very fatty, easy to apply and insulating plaster. 

Insulating Hemp Plaster made from Quicklime was very much the traditional way to insulate the inside of exterior walls, but with the modern and far more efficient options already discussed it has become less popular, although it is still occasionally used.

The Insulating Hemp plaster is still recognised as effective at improving the air tightness and insulation value of a traditional solid wall construction, without compromising or isolating the thermal mass properties of the wall.  The plaster sets rapidly with exposure to Carbon Dioxide and in the presence of moisture, hence it can be applied in thicker coats than conventional lime plasters.

Insulating hemp plaster should be applied at 35-50mm (in 20mm layers) on the inside face of external walls. The thermal conductivity of Insulating hemp Lime plaster is 0.07-0.09W/mk.  Although lower than other products discussed it does offer effective storage of heat and a good regulation of heat loss.

The insulated hemp lime plaster undercoat should be finished with Fine Stuff lime plaster, after the undercoat has fully dried. A hydraulic lime stipple / slurry coat should be applied first to smooth/ engineering bricks.

Decorating Insulating Lime plaster and renders – It is important that all finishes remain vapour permeable.  If they do not then trapped moisture might eventually build up to affect thermal performance.  A number of decorative finishes are affective at retaining breathability and are all available from Womersley’s Mineral paints, Natural Emulsions and Lime Wash.