Background and Methodology

As part of the International Energy Agency’s (IEA) "Solar Heating and Cooling" implementing agreement, the working group "Advanced Housing Renovation with Solar and Conservation" Task 37 was set up with the goal of describing renovation standards that are possible today, looking into and discussing new developments and implementation strategies at an international level. The focus is on joint national and international renovation projects in residential buildings whose energy consumption for heat and cold supply (space heating, hot water, auxiliary systems, and ventilation) was to be reduced by a factor of four below the national standard [1, 2]. As most of the participating countries are located in moderate or cold climates the focus is on the energy for heat supply.

In new buildings the so called “passive house technology” with an energy demand for heating of 15 kWh/m2KFAa could be stated as state of the art even though a thorough quality assurance is needed to achieve this goal. An energy supply for these buildings based on locally produced renewable energy in order to achieve net zero energy buildings is shown in various demonstration projects [3]. The development of concepts and their application to the existing building stock is the core working program of the IEA Task 37.

A common understanding of energy terminology and areas related to these parameters is a prerequisite for a successful work on an international level. UE indicates energy used in the building, EE indicates end energy at site including distribution and storage losses e. g.; PE indicates primary energy using national conversion factors for heat and electricity. The following definitions were used for area related energy characteristics: The heated net floor area NFA for the measurement analysis and Ause as an artificial area derived from the heated gross volume Ause = 0.32*V in energy calculations related to the German building code EnEV. In table 2 both areas are given, in some cases there is a significant difference. KfW40 and KfW60 indicates an primary energy demand of 40 kWhPE/(m2Ausea) for heating and DHW or 60 kWhPE/(m2Ausea) respectively. It’s a standard set by the German Kreditanstalt fur Wiederaufbau KfW. The 3-Liter-house aims for 30 kWhPE/(m2Ausea) with the same reference areas. The passive house standard is defined as 120 kWhPE/(m2NFAa) for the total energy consumption including all electrical household appliances, the heating energy demand is limited to 15 kWhUE/(m2NFAa). The zero house approach uses the same calculation scheme as the passive house standard but includes a full renewable supply on an annual balance level.

An analysis of measurements taken for completed renovation concepts provides the basis for further developments of energy efficiency measures and energy supply concepts. This paper focuses on the analysis of energy consumption and supply systems in realized projects.

1. Projects

Within IEA Task 37 more than 25 buildings from Europe and Canada will be documented and analyzed. Due to the availability of detailed measured data the German subset of buildings was chosen for a more detailed analysis. Tab. 1 shows the German buildings documented in this study. Some of the projects presented here were promoted as part of the German Funding Program ENOB, some of them as part of dena’s pilot project "Niedrigenergiehaus im Bestand" ("Renovating for low energy consumption") [4, 5].

Table 1: An overview of the German projects studied in IEA SHC TASK 37.

Project

Specifics

Owner / planner

Institute responsible for measurements

Rislerstrasse 1 — 5, 7 — 13 Freiburg

KfW40 and KfW60 standard

Owner: Freiburger Stadtbau GmbH Architect: B. Thoma — G. Henninger-Thoma Building services / energy concept:

Lenz / Stahl + Weifi

ISE

Roter Block Freiburg

Protection for facade

Owner: Freiburger Stadtbau GmbH Architect: Huller, Banzhaf + Partner Building services / energy concept: Fischer / Stahl + Weifi

ISE

Blaue Heimat Heidelberg

"Zero" house

Owner: GGH-Heidelberg

Architect: J. Gerstner, Heidelberg

Building services / energy concept: solares bauen

GmbH

ISE

Hoheloog-

strasse

Ludwigshafen

Passive house renovation

GAG Ludwighafen

Building services / energy concept: PHI

PHI

Tevesstr.

Frankfurt

Passive house renovation

AGB Frankfurt Architect: Grenz/Rasch

Building services / energy concept: Baumgartner/ PHI

PHI

Guter Hirte Ulm

Vacuum

insulation

Catholic congregation of Bofingen Energy concept: IBP

ШР

Freyastrasse

Mannheim

"3-liter house"

Owner: GBG Mannheim Energy concept: IBP / IGE

IGE / IBP

The buildings studied were renovated from 2003 — 2007. In the process, primary energy demand for heating and domestic hot water was reduced on the average by 80 — 90 %, which was around 50 % below the current requirements of the German building directive EnEV (Fig. 1). Furthermore, in some projects more ambitious goals, such as zero-energy concepts (Blaue Heimat, Roter Block), the passive house standard (Hoheloogstr., Tevesstr.), or the 3-liter standard (Freyastrasse) were pursued. During renovation, no one was living in the houses [6], [7] and [8]. The key building data are listed in Tab. 2. The measurements were evaluated for Rislerstrasse, Blaue Heimat and Freyastrasse [9], [10], detailed measurements are ongoing for all projects.

Подпись: primary energy demand according EnEV [kWh/m2Ausea] 400 Fig. 1: Comparison of calculated primary energy demand for heating, hot water and electricity for fans and circulation pumps in Rislerstrasse, Freyastrasse and Blaue Heimat

The two buildings in Rislerstrasse are three-storey residential complexes built in 1961. Similar layouts and designs allow us to compare the KfW40 energy standard, which was the goal for Rislerstrasse 1 — 5, to the KfW60 standard for Rislerstrasse 7 — 13. The main difference in these two buildings is the ventilation system. The building with the KfW40 standard has an air exchange system with heat recovery, while the KfW60 building has a simple exhaust ventilation system. A 60 kW gas-condensing boiler provides heat with the support of a solar thermal system (24 m2 and 29 m2 with 750 l of buffer storage, 500 l hot water tank).

In Heidelberg, Blaue Heimat is a three-story residential building constructed in 1951 to round off a block; it underwent thorough renovation. The energy renovation concept includes thermal optimization of the building envelope, the installation of a central air exchange system with heat recovery, and a gas-fired cogeneration unit (50 kWel/80 kWth) with a 3000 l buffer tank. This serves two not yet renovated neighbouring buildings as well. The goal was to offset all carbon dioxide emissions over the year to become a "zero house" [7]. Two 92 kW low-temperature boilers were already installed and were retained to cover peak loads. Radiators distribute heat into the rooms.

The project at Freyastrasse 42 — 52 in Mannheim are two-story buildings from the 1930s designed as terraced houses. Each unit has a separate air exchange system with heat recovery. Various systems were used and investigated for the distribution of heat. Overall, five types of systems were studied: three air heating systems with various control systems; a radiator heater; and a panel heating system. A cogeneration unit (Stirling motor 0.85 kWel/6 kWth) and a 185 kW gas-condensing boiler, both of which were installed in an adjacent building, provide heat. Hot water comes from an instantaneous system to reduce losses in storage and distribution.

Measurements were based on the monthly readings of heat counters and power meters (Rislerstrasse 05/06 and 06/07; Blaue Heimat 06/07 [9]) as well as on detailed measurements (Freyastr 05/06 [10]). The heated floor area was used for comparisons of specific consumptions (see Tab. 2). Fig. 2 shows values measured for consumption of useful energy, end energy, and primary energy for heating, hot water, auxiliary energy, and ventilation. Fig. 3 shows the energy flow chart.