Guideline 1 - Goals / National building requirements
National building requirements
Before setting the goal(s) for the renovation of a building, it is important to check whether the renovation complies with the building regulations in the specific country. Be aware that in some countries building regulations are laid down by federal or national authorities, while in other countries building regulations are also set by regional or local authorities, e.g. in Belgium.
Remember also to check district plans, covering land use/zoning questions and similar. Such plans may contain restrictions to the expression of the building (external architecture). Further restrictions are applied to listed and worth preserving buildings, where national or local authorities have to be consulted before deciding to change the building.
National building regulations contain rules to follow when renovating a building, all implementing and complying with the Energy Performance of Building Directive (EPBD) (Directive 2010/31/EU). This means setting cost-effective mimimum requirements for the energy performance of the building after renovation. In some countries requirements are only stated for major renovation, involving a number of measures, or for renovating building installations (ventilation systems and similar).
EPBD specifies major renovation as renovation of a building where the total cost of renovation relating to the building envelope or the technical building systems is higher than 25 % of the value of the building, or when more than 25 % of the surface of the building envelope undergoes renovation. In some countries major renovation is specified as renovation of more than e.g. 1000 m2 of floor area. Other countries defines two levels of major renovation, where at first level, defined as refurbishment of e.g. more than 25 %, 50 % or 75 % of the building envelope (and eventually the building installations), requirement for new buildings is to be followed (Concerted_Actions, 2013) (Concerted Action, 2016).
In some countries following the EPBD approach of major renovation (25 % limit), there may (e.g. Italy) or may not (e.g. Estonia) be requirements for renovation projects covering less than 25 % of the building envelope (Concerted Action, 2016). In the latter case, this means that a building element can be installed with the same energy performance as the one being replaced.
Gradually, national building regulations include requirements to be followed for all kind of renovation projects, no matter the size. This means that if only a part of the building is renovated, e.g. the external wall, it sets requirements for this specific building element and the joints to surrounding building elements, e.g. the foundation. Typically, requirements are given as a maximum U-value for the building element, expressing the maximum heat loss allowed (or the minimum thermal insulation performance of the building element). These requirements may vary between different parts of a country, based on climatic zones. If the country is divided into climatic zones, the U-value requirements may vary from one climatic zone to another. In some countries, the specific level of requirements (U-values) are dependent of the type of building (dwelling, office, production etc.)
In some countries, e.g. Denmark, the U-values are not mandatory to fulfil if lack of economic viability or moisture safety can be documented, but viable, safe measures getting as close as possible must be complied with. In other countries, e.g. Switzerland, the U-values are mandatory and they are set to ensure thermal comfort and a condensation-free surface. Be aware that to get a building energy certificate (or energy label), which is not mandatory when renovating a building, a full building analysis is often required.
National building regulations also put restrictions concerning fire resistance, indoor climate (comfort), pollution from building materials, moisture conditions and acoustric conditions that could be of relevance when renovating historic buildings, as it might set limitations for the use of internal insulation, if no further actions are taken. Example: when adding internal insulation to the external walls, even when it is a capillary-active system, containing no vapour-barrier, the building normally becomes more airtight, at least in window reveals. This could in some cases reduce the air change rate below the required level and – depending on the user behavior – increase the relative humidity to a critical level if no further actions are taken. When it comes to fire resistance, there are different rules among European countries regarding the kind of insulations systems that are allowed, some of which might give rise to toxic smoke if a fire breaks out.
Any kind of renovation has to comply with at least the level of requirements that was set when the building was constructed. However, the renovation also includes e.g. replacement of the ventilation system, then the requirements of the present building regulations are to be complied with for this specific replacement.
For listed and worth preserving buildings, building permits can be obtained with less strict requirements. This means that renovation can be done without fulfilling the same level or extent of improving the energy efficiency if this cannot be done without affecting the architectural and cultural heritage. This is often the case when considering insulating external walls of existing buildings, especially in the case of buildings having both worth preserving inner and outer surface of facades. In such buildings other measures such a replacing the heating or ventilation system are often easier to implement without affecting the facades or structural parts of the building. In any case, local or national authorities responsible for listed and worth preserving buildings have to be involved to ensure that a renovation project including internal insulation is allowed to be carried out.
Each of the EU Member States has to a certain extent prepared a long-term national/regional building renovation strategy for mobilising investment in the renovation of residential and commercial buildings. This is required to comply with the Energy Performance of Buildings Directive (EPBD) together with the Energy Efficiency Directive and the Renewable Energy Directive (Castellazi, Zangheri, & Paci, 2016). Details about the progress of implementing the EPBD can be found in the reports from Concerted Action: Energy Performance of Buildings (Concerted_Actions, 2013) (Concerted Action, 2016).
No detailed descriptions of national building regulations are given in this guideline as these may change from time to time. Further information is to be found at the relevant authorities in the specific country. Links to authorities in some of the countries can be found e.g. in the Concerted Action country reports (Concerted Action, 2016).
The RIBuild web tool contains the output of numerous hygrothermal simulations done as part of the project, based on a probabilistic approach. Simulations are based on 1 m2 of external wall, disregarding thermal bridges although these have a rather large effect of the behaviour of the wall in the case of internal insulation. Therefore, when it comes to checking whether a specific solution complies with the relevant building regulations, a more detailed calculation of the U-value for the whole wall is required, including thermal bridges.