As a building material, locally sourced (or possibly newly quarried), reclaimed stone may be a viable option but suffers from the drawback that stone itself has virtually no insulating value.
This can obviously be overcome by including sufficient insulation within the rest of the wall construction but it does tend to lead to a very thick wall with all that that implies for reduced floor areas. This is particularly true if the stones are thick or not evenly dressed. A wall thickness could easily be over 600mm. This has implications for such things as the available floor area, the width of foundations and how much light and view is available through windows.
There is an issue about embodied energythe total amount of energy it takes to make a material (or a building). See more on embodied energy with stone walls and using a lime mortar reduces the amount of embodied energy compared with a normal cement mortar.
If you are converting or repairing an existing stone building then there are several options for the insulation
1. apply insulation externally and use the mass of the stone for thermal stability (this is not often an option because the planners will usually want to see the external stone appearance left as it is.
2. Insert a timber frame inside the stone walls and install insulation within its thickness.
3. Spray polyurethane foam on the inside of the stone walls. This not only provides insulation but also seals up the small gaps between stones and mortar which can cause air infiltration. The foam can then be plastered or dry lined. Poyurethane foam has a good insulation U valuemeasurement of how much heat escapes (or gets in). The units are W/sq.m./°c. see Insulation properties of 0.022W/m²/ºC. See table
In any case you will need to apply 20 – 30 cm. of insulation to make a serious impact on heat losses.
Which course to take depends on several factors
- with an old building such as a barn where there may be a minimum of internal walls or structure (in other words a large empty space) you will probably need to insert an internal timber frame anyway. This is option 2 (above).
- if external walls are in poor condition they may benefit from extra support from insertion of a timber frame. A structural engineer will advise on this. Option 2 again.
- with a building which has lots of existing solid internal walls such as a house it makes more sense to go for option 1 if planning allows because of the better insulation achieved.
- if the stonework is rough, irregular and prone to air infiltration and possibly driving rain then option 3 will tend to seal and level out the surface. If the internal surface is very irregular, often the case with barns built of cheap undressed local stone, you get a thicker average layer of insulation with foam without the total wall thickness increasing.
Arguably the down side of using petrochemically produced foam is outweighed by its higher insulation value and the increase in space within the building. Furthermore, stone buildings tend to be in areas where the life of buildings is likely to be greater than elsewhere, mainly for aesthetic or conservation reasons, thereby diluting the detrimental effects of a one-off use of the foam.
Insulators such as paper, cork and wool should not be placed in contact with external surfaces such as stone which may be damp.
The Building RegulationsThese are the mass of regulations that cover safety, health, welfare, convenience, energy efficiency etc. in the way buildings are constructed. Not to be confused with Planning consent (which is more to do with whether you can put up the building in the first place). See more on the regulations part AThe Approved documentsApproved documents (England) are detailed publications which come under the English Building Regulations. They are based on tried and tested methods of building and if you follow them you are assured of complying with the Regs. The equivalents for Scotland are the Technical HandbookUnder the Scottish Building Regulations, the Technical Handbook gives construction principles, which, if you follow them guarantee compliance with the Regulations, for Wales: the Approved documents (Wales), and for N.I. the Technical BookletsUnder the Northern Ireland Building Regulations, the Technical Booklets give construction principles, which, if you follow them guarantee compliance with the Regulations, (England) part A, deals with building structures covers the structure of a building. This Approved Document goes into a lot of detail for traditional masonry buildings but almost none for timber frame, steel frame, earth building SIPsStructural Insulated Panels - prefabricated (usually in a factory) timber panels often forming part of an integrated building system and aimed at fast site erection. see more on SIPs etc. For these you will need to consult a structural engineer (while SIPs structures are usually handled by the manufacturer)
With most forms of construction there will be implications concerning fire safety. These are covered in the Building Regulations and you can see examples of how to conform with these in Part BThe Approved documents, (England) part B, deals with fire (Fire Safety)
Site preparation and resistance to contaminants
This section, Part CThe Approved documents, (England) part C, deals with Site preparation and resistance to contaminants (C1) and Resistance to Moisture (C2), covers site remediationthe term applied to the method of dealing with pollutants and contaminants in the ground. The Building Regulations cover this in detail. See info about Approved Document C – Site preparation and resistance to contaminants and moisture along with protection from nasties which might affect the construction and occupants such as damp, rain, radon etc. There is an abridged version of the Approved Document specially for houses.