Analysis of the economic viability of energy efficient building
In this article we intend to summarize the conclusions obtained by this interesting technical study carried out by Ecofys for the Sustainable Construction Working Group of Fundación Entorno-BCSD Spain. In it, a dynamic simulation of the energy behavior of several buildings for residential and tertiary use is carried out in different scenarios as well as an economic feasibility study of the different proposed improvement solutions.
Objective and scope of the study:
Two types of buildings are analyzed, one for residential use multi-family housing with 3 floors and another for tertiary use of offices with 14 floors, in two different building periods (buildings that are governed by the basic standard NBE-CTE-79 and in a second case by the Technical Code CTE-06), and in three different climatic zones Madrid (D3), Barcelona (C2) and Santander (C1), the total number being 2x2x3 = 12 different scenarios.
For each of the scenarios, the study proposes the application of a series of improvement measures aimed at obtaining buildings with a high energy rating, always starting from those hypotheses or situations that can be assumed and of course technically and economically feasible in each one of them. the situations. These improvements are grouped into three groups: on the one hand, passive solutions aimed at reducing energy demand (step 1) are included, on the other hand those solutions that involve the application of renewable energies (step 2) and finally introducing heating equipment, energy efficient cooling and / or lighting (step 3). These three steps make up the proposal that the study calls the energy triad. In this way, two cases or energy concepts are studied, the case CE 1 that includes only the measures of step 1 (reduce demand), and the case CE 2 that includes the measures of steps 1, 2 and 3 (reduce + renewables + efficiency).
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Existing multi-family dwellings.CASE 1:
Proposed improvement measures for existing multi-family dwellings:
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CASE CE 1:
Improvement of the thermal insulation of facades (9 -10 cm.)
Improvement of the thermal insulation of roofs (12 cm).
Replacing the windows (New: frame U = 2.2 with double glass)
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CASE CE 2:
Thermal solar energy covering 60% of solar contribution.
Replacement of existing individual boiler for DHW and heating by:
DHW: Individual gas heater.
HEATING: High efficiency heat pump (COP = 3,2).
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Results obtained: Energy savings (Graph 1) and CO2 reductions (Graph 2)
New multi-family housing.CASE 2:
Proposed improvement measures for new multi-family housing:
CASE CE 1:
Improvement of the thermal insulation of facades (5-6 cm) compared to that determined by the CTE.
Improvement of the thermal insulation of roofs (4 cm) compared to that determined by the CTE.
Replacing the windows (New: frame U = 2.2 with double glass)
CASE CE 2:
Thermal solar energy covering 60% of solar contribution.
Reference case with individual gas combi boiler and individual air conditioning (EER = 3), it is proposed to replace by:
DHW and HEATING: Centralized biomass boiler.
COOLING: High efficiency centralized heat pump (EER = 4).
Diffusion of cold and heat by underfloor heating.
Results obtained: Energy savings (Graph 1) and CO2 reductions (Graph 2)
Existing office buildings. CASE3:
Proposed improvement measures in existing office buildings:
CASE CE 1:
Improvement of the thermal insulation of facades (9-10 cm). Initial state without insulation.
Improvement of the thermal insulation of roofs (12 cm). Initial state without insulation.
Replacement of windows (New, frame U = 5.7 with double glass (U = 1.4 and g = 0.42) with low emissivity coating,
initial state (frame U = 5.7 and double glazing (U = 2.7 and g = 0.76).
Improvement with automatic ventilation system at night hours.
CASE CE 2:
RENEWABLE:
Photovoltaic solar energy on the roof.
AIR CONDITIONING:
Replacement of the existing centralized gas boiler and air-water chiller plant by:
Centralized biomass boiler and more efficient air-water chiller plant.
Results obtained: Energy savings (Graph 1) and CO2 reductions (Graph 2)
New office buildings. CASE 4:
Proposed improvement measures in new office buildings:
CASE CE 1:
Improvement of the thermal insulation of facades (5-6 cm) compared to that determined by the CTE.
Improvement of the thermal insulation of roofs (4 cm) compared to that determined by the CTE.
Replacement of windows (New, frame U = 2.2 with double glass (U = 1.4 and g = 0.42),
initial state with hole transmittance value determined by the CTE.
Improved by increasing the efficiency of the RITE of the heat recovery system (44-85%).
CASE CE 2:
RENEWABLE:
Photovoltaic solar energy on the roof.
AIR CONDITIONING:
Replacement of the existing centralized gas boiler and air-water chiller plant by:
Centralized gas boiler with geothermal heat pump and radiant floor (hot and cold).
ILLUMINATION:
Lighting regulation system.
Replacement of T8 fluorescent luminaires with T5.
Results obtained: Energy savings (Graph 1) and CO2 reductions (Graph 2)
Most relevant conclusions of the study:
EXISTING MULTI-FAMILY HOUSING: Large energy savings can be achieved, between 72% and 78%, so that the improvement measures that contribute the most to this objective are the thermal insulation of the façade and roof and the replacement of windows together with the implementation of solar thermal energy. , which, as indicated in the document, is the measure that achieves the greatest reductions.
NEW MULTI-FAMILY HOUSING: In this case, energy savings oscillate between 24-39% of the total energy consumption of the house, being again the thermal insulation of facades and roofs together with the improvement of the windows the measures that contribute the most. However, the achievable scenario would lead us to a building with the highest energy rating in all climatic zones analyzed, so that significant reductions in emissions are achieved, of between 78-97%, which would be achieved by the inclusion of a boiler biomass for DHW and heating.
EXISTING OFFICE BUILDING: Savings of between 62% and 64% in energy consumption can be achieved, so that the improvement measures that contribute the most to this objective are the thermal insulation of the façade and roof and the replacement of windows, together with the improvement of the system. of air conditioning. The reduction of emissions reaches between 64-67%, with the biomass boiler being the measure that contributes the most. The building thus rehabilitated can achieve an energy rating B.
NEW OFFICE BUILDING: The range of improvement in energy consumption ranges between 57% and 63%, so that the improvement measures that contribute the most are the thermal insulation of the facade and roof and the replacement of windows, and the increase in the efficiency of the system of heat recovery, the regulation of the lighting and the improvement of the air conditioning system. Emissions can be reduced by between 52-55%, the most important measure being the use of a geothermal exchange system since it generates a large increase in the total efficiency of the air conditioning system. The newly built office building with these criteria could achieve an energy rating B.
With respect to economic feasibility study, presents very interesting conclusions and reflections, which are summarized in the following table:
Article prepared by Jose Luis Morote Salmeron (Technical Architect - Energy Manager - Google plus Profile) Access to their website HERE, in collaboration withOVACEN.
