Insulate background information

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Buildings

Building assessment

Building assessments give information about the condition of buildings as well as on the need for and anticipated cost of renovation. Major repairs and renovation foreseen within the next five to ten years as well as need for more in-depth building inspections are typically included in the building assessment report.

Structural engineering experts as well as experts in heating, plumbing, ventilation and electrical installation are needed for performing a completed building assessment. It is usually recommended that first assessment should be performed when the building is about 10 years of age. After that, the assessment should be updated every five to ten years. Energy audits and related assessments can be performed at the same time.

Building assessments are commonly conducted as building walkthroughs utilizing checklists and other non-destructive assessment methods. While some simple measurements can be taken, the assessment is mainly based on a visual evaluation of the building’s condition and of the need for renovation. Building assessments may be further complemented by interviewing or surveying building occupants to collect information and perceptions about the building. There are some common guidelines for ordering, performing, and reporting building assessments, and in some countries, building owners may apply for financial aid to cover the costs related to building assessments.

Building inspections

If persons conducting building assessments deem it difficult to assess the condition of some parts of the building, they will propose a more detailed inspection. On one hand, building inspections give more precise and detailed information about the condition of critical parts of the building. On the other hand, they give information that will help in planning renovations and in choosing appropriate renovation methods. Typically, building inspections can focus on:

• Structures or structural components, such as outer walls, balconies, rooms with a floor gully, roofs
• Plumbing system
• Electrical systems
• Heating systems
• Ventilation systems
• Indoor environmental quality (IEQ)

Professional education and experience is required for performing these inspections. The inspector should also have proper tools and equipment for taking and analyzing samples.

The methods and procedures of the inspection vary depending on the inspection target. There are several methods and combinations of methods which inspectors can use in their work:

• Studying design plans and other documents
• Visually-based inspection
• Structural openings and other destructive methods
• In situ measurements and tests
• Illustrations and viewing of structures and piping
• Taking samples and analyzing them at a laboratory.

In the following, some structural measurements are described which can be included in building inspections that could also be related to IEQ.

Surface temperatures

Measuring surface temperatures of the outer walls helps tracking spots with poor thermal insulation, heat/cold bridges, and air leakage. Surface temperatures can be measured using thermographic camera or surface temperature meters. Surface temperature is usually presented as a thermal index (TI), which takes into account outdoor and average indoor temperature at the measurement point. According to the Finnish Housing and Health Guide (Asumisterveysohje 2003), a good level is TI ≥ 65 and an adequate level is TI ≥ 61.

Airtightness

Airtightness of the building envelope is usually determined by so-called blower door tests. The special equipment (blower door) is installed on one door and all other openings (doors, windows, chimneys, ventilation vents) are sealed. The equipment creates 50 Pascal under or over pressure into the whole building and measures leaking air. It also calculates the airtightness value, n50 or air leakage value q50. If some other value than q50=4 m3/h m2 is used for calculating the E-value of the building, the airtightness of the building should be measured. Measuring the airtightness of an entire apartment building is quite difficult and laborious work, since all openings in all the apartments should be sealed. It is also possible to measure airtightness of one apartment, but the results will not be very reliable because of some air leakages through the walls between apartments.

Air change rate

Measuring air change rate is a basic part of an inspection of the ventilation systems. The inspection includes visual inspection of the condition and cleanness of the air channels, vents, and air supply units. If the building is equipped with mechanical ventilation, the air exchange rate could be assessed by measuring air flows from the exhaust air vents. It is quite difficult to assess the air change rate if the building has natural ventilation. In such cases, air change rate can be assessed by using a so-called tracer gas method. It is commonly agreed upon that the air change of an apartment should be at least 0.5 m3/h in all the rooms (air change rate 0.5 l/h).

Pressure difference

Balancing the ventilation is critical for managing the pressure difference between outdoor and indoor air. Also the temperature differences between the indoor and outdoor as well as the outdoor conditions, such as wind, affect the pressure difference.

High over pressure between the outdoor and the indoor may lead to moist indoor air transferring into the structures and resulting in condensation, while high under pressure may lead to all the impurities of the structures and surrounding environment (e.g. radon from the soil underneath the building) being sucked into the indoor air. Table 2 shows the acceptable pressure differences in the different types of ventilation systems, according to the Finnish guidelines. [1]

Ventilation system	Pressure difference	Notes
Natural	0...-5 Pa against outdoor 0 Pa against staircase	Pressure differences vary a lot enclosed to weather
Mechanical exhaust	-5...-20 Pa against outdoor 0...-5 Pa against staircase	Pressure differences vary a lot enclosed to weather
Mechanical inlet and exhaust	0...-2 Pa against outdoor 0 Pa against staircase	Pressure differences vary a lot enclosed to weather

Energy efficiency

Energy efficiency and energy consumption

Energy efficiency (EE) is a commonly agreed method of presenting energy consumption in a comparative form. It is based on the so-called standard use of the building as well as on certain components, such as ventilation, warm water, lightning and indoor temperature. Energy consumption is also calculated using commonly agreed outdoor climate values, for instance the climate zone 1 (Helsinki-Vantaa) in Finland. The energy efficiency value (E-value) is based on the calculated total energy consumption multiplied with the energy source coefficient. Rules for calculating E-value vary across Europe. In Finland, building energy efficiency used to be presented with the so-called ET value before adopting the EE value. The two values are not comparable.

Measured energy consumption is another way of presenting the energy consumption or energy efficiency of a building.

Factors affecting EE

Energy consumption is in principle the energy used for heating, minus the internal (people, devises) and external (solar) heat gains.

There are several factors affecting the energy efficiency of buildings:

• Structures facing outdoor (walls, roofs, floors, windows, doors); primary depending on thermal resistance of structures (U-values)
• Airtightness of the building envelope; low airtightness increases air leakages and energy losses
• Ventilation; sufficient ventilation to maintain good indoor air quality (IAQ), but not too efficient to cause heat loss (heat recovery system in mechanical ventilation systems minimizes heat loss)
• Energy needed for warming up water
• Energy needed for lighting
• Energy needed for electric devices inside the building
• Solar radiation through windows depending on various factors (orientation, shading, type of windows, etc.)
• Heat gain from people, lightning and electric devises inside the building (warm up the indoor temperature and, therefore, reduce the energy needed for heating)
• Efficiency of the technical systems (heat loss in the heating systems etc.).

Table 1 shows how the acceptable U-values for building components have changed in Finland during the past decades.

Table 1. Acceptable U-values and other boundary values in the energy consumption calculations.

U-values on building component	1976	1978	1985	2003	2007	2010	2012*
Outer wall	0,4	0,29	0,28	0,25	0,24	0,17	0,17
Roof	0,35	0,23	0,22	0,16	0,15	0,09	0,09
Floor	0,40	0,40	0,36	0,25	0,24	0,17/0,16	0,17/0,16
Window	2,1	2,1	2,1	1,4	1,4	1,0	1,0
Door	0,7	0,7	0,7	1,4	1,4	1,0	1,0
Other boundary values for calculation
n50-value (airtightness)	6	6	6	4	4	2	2
Annual coefficient of efficiency of heat recovery	0	0	0	30%	30%	50%	45%
Compensation possibility in heat flow of envelope	0	0	0	10%	20%	30%

*The total energy consumption will be multiplied with coefficient depended on energy source. The limit values of 2012 are leading average 20% energy demand compared with 2010 values.

Possibilities to improve EE

The Housing Finance and Development Centre of Finland (ARA) has listed 16 actions for improving energy efficiency:

1. Improving windows by refurbishing
2. Replacing windows
3. Improving outer walls by adding thermal insulation, at least 50 mm
4. Improving outer walls by adding thermal insulation, at least 100 mm
5. Improving roof by adding thermal insulation, at least 150 mm
6. Adjusting ventilation (basis adjustment)
7. Building new heat recovery system into the ventilation system
8. Joining to district heating or zone heating system
9. Renewing heat distribution center of real estate
10. Renewing oil-fired boiler or oil burner
11. Replacing old room heating or water circulating heating by electricity with new central heating by geothermal heat pump
12. Supplementing old electricity room heating with air heat pump
13. Replacing old heating system with new low emission pellet boiler
14. Installing apartment specific water meters
15. Adjusting heating grid (basic adjustment)
16. Supplementing old electricity or oil burner system with solar heating system

Energy audit

An energy audit must be included in all new building permits (as of 2008). The audit includes the source information form, final results of the calculations, regular calculations as well as the energy performance certificate (EPC). The survey for new buildings includes the following parts:

1. Report that the thermal losses of the building fulfill existing regulations
2. Calculation of the electric power of ventilation system
3. Estimation of the heating energy needed in the building
4. Estimation of the summer indoor temperature (and cooling energy need, if needed)
5. Estimation of the actual energy consumption of the building
6. Energy certificate, including the energy class (E-value A….E).

There are limit values for the E-value, based on different type and size of the building. The EPC is a tool for comparing the energy efficiency of the different buildings. The EPC with the E-value is based on properties of the building, not the current use of the building. In old buildings the EPC usually includes also the report of the actual energy consumption, but the energy class is only based on the calculations.

The EPC should be presented when applying for the building permits and when selling or renting the building or the apartment.

See also

• Insulate
• Insulate background information
• Insulate field results
• Insulate protocol and results
• Insulate publications and deliverables
• Insulate meetings and workshop