Energy performance of newly erected and existing buildings

Transcription

1 Title of the measure: Energy performance of newly erected and existing buildings General description The Decree of the President of the Republic no. 412/93 established a comprehensive framework for the energy performance evaluation of newly erected and existing buildings. The Decree values have been modified and updated by the approval of the EPBD and its implementing Decrees, especially L.D. n. 192/2005, DLgs 311/06 and DPR 59/09. With the adoption of Directive 19 May 2010, n. 2010/31/EU, the European Parliament has taken steps to recast the previous legislation in the field of energy efficiency in buildings by updating it in light of technical progress, and in the light of the achievement of the new objectives of 2020 which provide for a reduction of 20% of energy consumption. The L.D. 4 June 2013, n. 63 converted into Law August 3, 2013, n. 90 adopted - with a delay of a year - the Directive 2010/31/EU implementing and updating the Decree No. 192/2005. (see ITA 37) What is described below refers specifically to Article 8 of Presidential Decree No. 412/1993, repealed by DL 192/2005 (see ITA 37 where the whole new methodology for the calculation of the global energy demand is described) The Decree 412/93 set a number of principles and methodologies for the evaluation of: 1) Building and Thermal Equipment systems 2) Design norms for the Building shell 3) Thermal Equipment 1) Building and Thermal Equipment System This norm is based on the criterion of energy needs limitation for the system building + thermal equipment and provides guidelines for the calculation of limit values to the energy need for wintertime heating. These values can be stemmed and quantified through an energy balance accounting for: the amount of primary energy absorbed by the thermal system; the amount of solar energy received by the building, taking into account both the cold period and the warm one of the year (particular attention is given to the building location and orientation, with respect to the sun, the dominant winds, but also to the surface and to the disposition of windows);

2 free internal energy inputs (lighting, human beings); the amount of energy dispersed by the building shell and by the thermal system itself. Thus, a piece of thermal equipment is, as a whole, a plant devoted to the conditioning of milieus with or without sanitary hot water production, which includes heat production, distribution and use systems (excluding fireplaces, solidfuel-burning stoves, mono- family water heaters, but including individual heating equipment). The adoption of such a criterion (energy needs limitation) also implies a methodological approach to building design that takes into account: a) A global limit of energy needs by unit of heated volume and by degree-day (FEN), assuming that the internal temperature is kept at a constant value (20 C) all along the heating period. The parameters on which the building engineer and/or designer may freely play in order to limit the reference consumptions are: - thermal insulation (Cd coefficient) of the building shell, smaller than a predetermined value (for private buildings C dlim values remain unchanged, with respect to those defined by the pre-existing Law 373/76, which was integrally amended by the current law); - seasonal average global efficiency (η g ) (outcome of generation, distribution, regulation and heat emission efficiency) greater than predetermined values *; - thermal re-use of the re-circulated air - orientation and sizing of glazed surfaces b) The introduction of minimal efficiency values for boilers newly installed or changed c) The introduction of minimal values for the thermal insulation of thermal pipes of newly or restructured thermal plants. The value of FEN has to be calculated according to UNI norms 10379, and and has to result smaller than the value determined by the following formula: [ ( )]

3 C dlim = limit heat loss coefficient [ ]; n = number of air re-circulation [h -1 ]; Ir = average value of the solar radiation on a horizontal plane [ ] ; K u,a = coefficients of real use of solar and internal inputs; η g = seasonal global average efficiency; 86.4 = thousands of seconds in a day [ ] ; 0.34 = value showing the air s specific heat multiplied by its density [ ]; 0.01= conventional value of the solar energy absorption surface of total per volume heated unit [ ]; The calculation of the volumetric heat loss coefficient must be calculated using the UNI 7357 and must not exceed the values that will be set by the regulations referred to paragraphs 1 and 2 of Article 4 of the Law of 9 January 1991, n. 10. Waiting for the enactment of these regulations, the limit values of this coefficient will still be determined in accordance with the provisions of the Decree of the Minister of Industry, Commerce and, in consultation with the Minister of Public Works of 30 July 1986 published in the Gazzetta Ufficiale of 20 October 1986, n Maximum allowed C d -values depend on: - the ratio A tot /V tot of the building (total external loss surface/total heated volume); - the strictness of the climatic zone expressed in degree-day (DD), that is the sum of positive daily differences between the milieu temperature that is assumed to be equal to 20 C (Art 4, Dpr n 412/1993) and the average outdoor daily temperature); to this end, the Italian territory has been divided in 6 climatic zones (A, B, C, D, E and F), according to the number of degreedays, whose values have been updated by D.P.R. 412 itself. They range from less than 600 degrees-day to more than 3000 (Measure ITA12). These values may be easily drawn from ad hoc-tables and graphs (art. 2 and 9). The design of the thermal equipment (both new systems and restored ones) must also take into account: - the separation of the space heat generator from the sanitary water heater, because of the different features to the equipment (in terms of installed power and energy production times and duration); - the installation of devices for automatic regulation of the indoor temperature in single rooms or dwelling areas (in case there is a significant solar input), in order to avoid local overheating phenomena.

4 The technical plans for the above-described works are supposed to be attached in the technical documentation to be provided when applying for the building licence. 2) Design Norms for the Building Shell a. Contents of the norm The norms have completely modified the criteria of energy-design, introducing the concept of energy consumption containment of the "system building and thermal plant", based on a complete energy balance taking into account: - building insulation; - energy efficiency to the plant; - internal contribution; - solar contribution. Thus the previous parameters, on which the designer can operate in order to contain energy needs within the set limits, are increased. In fact, he can work on: 1. building thermal insulation; 2. average seasonal efficiency of heat generator; 3. thermal recovery of air changed; 4. exposure and surface of windows. However, the thermal insulation of the shell has to satisfy minimal energy consumption requirements. The norm sets limit values for global volume dispersion coefficient (C d ), which represents the thermal power loss for transmission for each heated volume unit and for each degree of difference between the internal and external temperature. b. Procedure to apply the norm The designer is supposed to: - define the limit value of C d, set by law for the building; - calculate the C d of the building; - check out that the calculated value is equal or less than the limit value set by law. The value of C d has to be calculated, as described in UNI (Italian Standard Norms), by reckoning the averages of the following formula:

5 = thermal power loss for transmission throughout the shell, calculated according to UNI 7357 (Watt); = gross volume of building heated, defined by the external surface (expressed in m 3 ); = internal temperature fixed by art. 4 of D.P.R. 412/93 (generally 20 C); = minimal external design temperature fixed by UNI 7357, depending on the place (i.e. the city of Rome = 0 C). C d limit depends on the following different variables: - S/V = ratio between the external surface and the gross volume (indicator of building compactness); - Climatic Zone stated by the law, depending on the degree-day. As a whole, we can allege that value of C d limit decreases from the colder climatic zone and increases while the building compactness decreases. This is due to the fact that for a certain quality of insulation the loss is greater whereas the compactness is smaller. c. Detailed measure description In order to correctly apply the measure, the designer should follow the procedure shown in the diagram below: Cd calculation and check of Cd limit set by the law d. The Cd limit The first step is to establish the Cd limit (C dlim ) value set by law. The limit values depend on the climatic zones (A, B, C, D, E, F) corresponding to different ranges of degree-day stated by the norms, and on the indicator of compactness to

6 the building (S/V). The C d limit values are reported in the following tables: Table 1: C dlim for household sector buildings (D.M.30/7/86), these values have been updated by the L.D. n. 192/2005(Measure ITA 24) Climatic Zone A <600 S/V <= S/V >= B C 900-1, D 1,401-2,100 E 2,101-3,000 F >3, Table 2: C dlim for buildings of industrial and crafts sector (D.M.23/11/826) these values have been updated by the L.D. n. 192/2005(Measure ITA 24) Climatic Zone A <600 B S/V <= S/V >= C 900-1,400 D 1,401-2, E 2,101-3, F >3, Cd limit value has to be calculated this way: - for 0.9>S/V>0.2 the value obtained by a linear interpolation of data reported in tables I or II, depending on the type of building; - for S/V<0.2 the values are set as those for S/V = 0.2; - for S/V>0.9 the values are set as those for S/V = 0; - for each Climatic Zone there is s a band of values of Cdlim. - the designer has to find the limit by an interpolation of Climatic Zone boundary values, which the building belongs to. For instance, for a building with a S/V < 0.2 and belonging to a Municipality with 2300 degree-day (E Zone) Cdlim will result equal to: C dlim = [( )*( )/( )] = 0.33 [W/m³K] e. The Cd limit calculation Once set the C dlim, the second step is to calculate the real Cd following the procedure

7 described in the technical norm UNI 735: Cd = Qtr / V * (Ti-Te) [W/m³K] Qtr = thermal power loss for transmission through the shell; V = building gross volume; T = internal design temperature set by law (20 C); Te = external design temperature set by a table of UNI 7357, according to the place (e.g. Rome = 0 C). To calculate the Qtr one has to know: Geometric measures of: - surfaces of transmission of each building component (i.e. the walls) which divides the space heated and another space in different conditions (A); - the thickness of different materials of the walls (si). Global thermal transmission coefficient (U) of each component to be calculated using the criteria set in the norms: - UNI 7357 for non-transparent walls (deducing the thermo-physics features of materials as stated in UNI and UNI 10355); - UNI for glass-walls. For glass-walls, further information is required about the following features: - surface of glass (Ag); - surface (Af) and features of the frame; - number of glasses (n); - thickness of the inter-spaces (and the type of gas included). Features of thermal conjunction (boundary area of different walls): - length (li); - thermal linear coefficient of loss (Yi) Laminar thermal exchange coefficient (for convection heat exchange) for the internal and external surfaces(uni 10344): - internal surface (all the walls) hi=7.7 W/m2K; - external surface:

8 a) external walls he=25 W/ m²k; b) internal walls he=7.7w/ m²k. Temperature of the space adjacent: - external space; - zone heated at a different temperature; - non-heated zone (T). For non-transparent walls (n-tw) the global transmission coefficient will be: Un-tw = [ (1/hi)+(S si/li)+ (1/he) ] - 1 For glass-walls (gw): Ugw = [(AgUg+AfUf)/(Ag+Af) Uf = thermal transmittance of the frame Ug = transmittance of glass = [ (1/hi)+(Srjdj)+(SRi)+(1/he) ] - 1 ri = resistance of glass j of n glasses Ri = thermal resistance i of n-1 inter-space Dj = thickness of j glass of n glasses Finally, the power loss for transmission will results as the sum of all the dispersions throughout all the parts of each type of wall: Qtr = [S Ugw (Ag + Af)+ S Un twan tw + SYili ] (Ti - T) [W] 3. Thermal Equipment The norm defines the average seasonal global efficiency of the thermal plant, defined as the ratio between the thermal energy necessary to the space heating and the primary energy consumption unit (including electricity). The average seasonal global efficiency (Eg), calculated according to the UNI norms 10348, results as the outcome of the generation, distribution, regulation and heat emission efficiency and it is supposed to be greater than the following value:

9 η g = ( log Pn)% Pn = nominal useful power to the heat generator(s) - that is (are) part of the single thermal equipment calculated in Watt. Moreover, the norm sets for the first time the following requirements, which have to be achieved by the thermal plants in case of restructuring or substitution of boilers: the boiler efficiency has to be higher than minimal values set in the enclosure E of D.P.R. 412/93 (depending on the boiler size and its outcome temperature); in collective thermal plants powered over 350 kw, the power has to be shared by at least two boilers, in order to improve their efficiency during low-working times; in the collective thermal plants, both space heating and sanitary hot water have to be provided from separated boilers; the thermal dispersion coefficient of the distribution pipes has to be lower than the values set in the enclosure B of D.P.R. 412/93; in collective thermal plants, whenever it is possible to identify buildings zone with different occupation factors, the distribution system should modulate heat supply to the latter, according to its occupation condition; the heat recovery of exhausted air, whenever a mechanical ventilating system exists. The substitution of heat generators must, furthermore, fulfil the average seasonal yielding efficiency value (η g ), defined as the ration between the thermal energy input to the power grid and the primary energy, including electricity. This value must not be less than the following one: η g > ( log Pn)% The calculation of the η g value must conform to the UNI norms stated in art. 2, clause 2 to the same law decree and must refer to the year working period of the thermal equipment, depending on each of the six climatic zones (A, B,C, D, E and F), as described in art. 9: A : 6 hours per day from December 1 st to March 15 th ; B: 8 hours per day from December 1 st to March 31 th ; C : 10 hours per day from November 10 th to March 31 st ; D: 12 hours per day from November 1 st to April 15 th ; E : 14 hours per day from October 1 st to April 15 th ; F : no limits (the working period to the thermal equipment must be from 5 a.m. to 11 p.m. anyway).

10 Public buildings and other such as schools, kindergartens, hotels, and swimming pools are not included in the provision for the thermal equipment working period limits. Only peculiar weather conditions can modify the mandatory working period over the above- mentioned limits (art. 9, clauses 3 and 5). 4. Thermal Plants Regulation and Metering This norm applies to newly erected buildings, whatever their destination is (residential, commercial, industrial or public), and to existing buildings to be restructured. The norm sets the following criteria for the thermal plant regulation and metering: - heating system serving new buildings has to be designed and installed in order that the tenant could install both a thermal regulation system and heat meters; - the collective thermal plants powered over 35 kw have to be equipped with a thermal regulation system, allowing the regulation of space temperature at least on two levels of temperature throughout 24 hours; - obligation of installing an internal temperature self-regulating system in the single heating zone, whenever there is a significant solar or inner input (20% out of the total energy requirement), in order to avoid local overheating effects. Impact evaluation Methods (Describe here methods used for the evaluation) Results (Describe here results of the evaluation) Ex-post evaluation direct CO 2 (kt) Energy (TJ) (Fuels/Electricity) Ex-ante evaluation direct CO 2 (kt) Energy (TJ) (Fuels/Electricity) Notes: 1) You might modify the years specified in this table, if the evaluation of your measure contains other years.

11 2) CO 2 and energy savings should be specified with respect to the reference scenario. If they are specified with respect to a fixed base year, e.g. 1990, and you cannot adapt to the requirements, please make a note in the measure description. 3) Please specify the energy savings separately for fuels saved and for electricity saved. CO 2 savings should only be for direct emissions from fuel combustion in the final sectors. For electricity please suggest in a footnote an emission factor per kwh. In the case of CHP please specify the reference towards which the savings are measured. Please fill-in the semi-quantitative impact measure table, too, for all measures and also give some explanations. Measure Impact Level low X medium high Interaction of measures The Decree is complemented by the Measure on limiting heating period (ITA 12) whereas its values and reference standard values have been modified and updated by first by the D.L. D.P.R. no. 551/99 (ITA 16) and then by the approval of the EPBD and its implementing Decrees, especially L.D. n. 192/2005 and L.D. 59/09 (Measure ITA24). The L.D. 4 June 2013, n. 63 converted into Law August 3, 2013, n. 90 adopted - with a delay of a year - the Directive 2010/31/EU implementing and updating the Decree No. 192/2005. (see ITA 37) Historical data The current legislative provision amends the old norms on energy savings in buildings, mainly consisting in the Law no. 373/76 and the corresponding application law decrees, concerning the size, regulation system, efficiency limits and piping insulation for heat generation systems for space heating, as well as the external temperature to be considered when designing the heating system installations. The previous design norms for the building shell where included in the Law no. 373/76, and its executive decrees (D.P.R. 1052/77, D.M. 10/3/77, D.M. 26/1/81), which are outdated nowadays, and have been wholly amended by the current decree D.P.R. 412/93. The criterion for old norms was based on: - limiting the thermal dispersion only throughout the building shell (Cd) - setting max generator's power by the following formula: Pmax = (Cd lim n) V * ( Ti - Te)

12 Pmax = max generator's power n = number of air's change V = gross volume of space heated Ti - Te = design temperature difference References The original Italian text of the Law no. 10/91 <<Norme per l'attuazione del Piano energetico nazionale in materia di uso razionale dell'energia, di risparmio energetico e di sviluppo delle fonti rinnovabili di energia Suppl. Ord. n.6 alla G.U. n.13 del 16/1/1991>> above described can be found at the following URL: The original Italian text of the Law n. 9/91 << Norme per l'attuazione del nuovo Piano energetico nazionale: aspetti istituzionali, centrali idroelettriche ed elettrodotti, idrocarburi e geotermia autoproduzione e disposizioni fiscali Suppl. Ord. n.6 alla G.U. n.13 del 16/1/1991>> also mentioned in the description above is at the URL: The original Italian text of the DPR n. 412/93 <<Norme per la progettazione, l'installazione e la manutenzione degli impianti termici degli edifici - Zone climatiche>> also mentioned in the description above is at the URL: