Following up my article published on the 9th of September I would like perhaps to continue with an example of how to introduce thermal insulation in a rehab job complying with the new Código Técnico de la Edificación (CTE) of 2007 New Spanish Building Regulations.
Once you have decided to carry out a rehabilitation job, if you are not absolutely certain about what you are doing, the best advice is to contact a professional and insist that his/her solution should comply with the Código Técnico de la Edificación (CTE).
Do contact you Autonomous Authorities and local Town Hall, as it is very possible that there may be an economic aid program for energy saving projects. These programs are held annually, with very short periods for applications to be made, so it is important to be informed and acting promptly.
The MITyC-IDEA, is the Action Plan and Energy Efficiency Savings 2008-2012 and includes a strategic move aimed at improving the standard insulation for homes.
Do contact 2 or 3 companies at least.
It is best to contact your local architect or surveyors that may offer independent advice on the feasibility of the various proposed solution, and provide you with an estimate of the savings obtained and a rough estimate of the final price.
Then do contact 2 or 3 companies at least to obtain estimates from, but making sure that the offers do include the involvement of all the necessary trades and when the finished job is handed over all work are integrated in the price given.
A practical case.
Let’s take an example of a hypothetical community of neighbours in the city of Madrid, (I have chosen a place with good low temperatures in winter and hot temperatures in summer for the sake of this example) consisting of 6 houses in a building block. The majority of owners decide in one of their annual General Meetings to improve the insulation of exterior walls.
The building was built in 1975 and is, therefore, is more than 30 years old, which means that during its construction no thermal insulation was placed into the cavity walls.
The president of the community obtains professional advice from an architect who decides that the best solution will be to insulate the external walls from the outside as the work will not interfere with the life of owners who don’t need to abandon their houses during the work.
Once the tender documents are prepared they are sent to three rehab companies and one is selected to carry out the works. The building works are done from the exterior with the aid of scaffolding allowing the staff direct access to work from the street.
Another solution it could have been to inject polyurethane foam into the cavity from outside, but the architect wanted to add an additional protection to the external wall.
The reduction of our heating requirements could be cut into half.
The building has the following features:
From the CTE we find that the Location is under a D3 climate zone, characterized by a harsh winter and quite hot summers. Albacete, Ciudad Real, Guadalajara, Lérida and Zaragoza are under the same climate zone.
Type of building: single housing block, 3 floors plus a ground floor, with 2 apartments per floor and 12 metres high. The surface of each house is 92 m2, and the glass surface of 10 m2 per dwelling.
The facade is a rendered brick wall and has an approximate area of 1,000 m2.
Assuming that there are 6 apartments in the building, the total surface of the housing facade is approximately about 100 m2, as it has an inner courtyard.
The heating system is that of a natural gas boiler works for 5 months a year, from November to March. In the building there is no installation of air conditioning, which does not mean that cooling is required in the warmer months. In fact, some users have installed small self-contained air conditioning in the lounge and master bedroom, which has not been taken into account in this study.
The annual energy demand, due only to heating, is 132 KWh/m2 per year or, a gas bill of about 895 € per dwelling.
The recommendation from the architect was to carry out a treatment on the four walls of building block incorporating insulation on the outside and a ceramic cladding on the external skin. The cladding would be fixed to the brick by metal anchor points at a distance not more than 80 cm between them.
The existing building is composed of the following skins going from outside to inside.
11,5cmm hollow brick rendered outside followed by a 4 cm cavity (No insulation) a 4 cm hollow brick and 1,5 cm of plaster inside. The thermal transmittance of the entire closure is “U” = 1.83 (W/m2.K). The thermal transmittance (“U” value) indicates the "ease" with which the heat escapes from a home. High values of “U” indicate bad insulation and lower “U” values indicate insulation.
We have added to this a 1cm of ceramic cladding and 5 to 6cm of thermal insulation with Thermal Resistance of 1,5 m2 K/w providing us with a thermal transmittance of all the enclosure of an “U” = 0.55 (W/m2.K) against the “U” = 1.83 (W/m2.K) obtained from our initial wall.
The result is a new facade which has managed to increase its thermal capability in 70% and the impact on the reduction of our heating requirements is approximately 35%.
Therefore, changing from a yearly expenditure on heating of 895 Euros to 585 Euros, this means an annual savings per household of 310 Euros.