Hello everyone,
below is the concept for our residential house regarding energy saving and the desire for self-sufficiency. Construction will start in spring 2014, and the planning is mostly complete. We would be very happy to receive suggestions, assessments, and comments.
Concept for a Self-Sufficient Passive House in Stages: The house is planned as a passive house meeting the PHPP requirements, so the building’s estimated final energy demand is around 15 kWh/m2/a (1.4 kBtu/ft2/yr). The heating load per square meter is at the required 10 W/m2 (3.2 Btu/h/ft2).
The building footprint is 10 x 11 m (33 x 36 ft), nearly two stories high with a 2 m (6.6 ft) knee wall. In total, this results in approximately 135 m2 (1453 ft2) of heated living space.
The following passive components will be implemented during construction:
The foundation slab will be insulated underneath with load-bearing foam glass (a system of panels and edge supports made of foam glass, not foam glass gravel). No screed or insulation will be added on top of the slab since the concrete will be polished and later waxed directly.
The ground floor ceiling will also be concrete, with a very thin cork layer on top for impact sound insulation, followed by screed that will also be polished and waxed.
The wall material will be one of the new insulating bricks with a thermal conductivity (lambda) of 0.07 W/mK and a masonry thickness of 49 cm (19 inches). All thermal bridges are documented and executed accordingly.
The windows and doors will have triple glazing, just under the required Uf or Ud values of 0.8 W/m2K (0.14 Btu/h·ft2·°F). Ideally, I would like aluminum windows with integrated internal sunshades (e.g., from Schüco), but as I am still waiting for pricing, wood-aluminum windows are also an option.
The roof will be a prefabricated system roof with TGI joists, achieving a U-value of 0.1 W/m2K (0.018 Btu/h·ft2·°F). The orientation is planned east-west with a 15-degree pitch.
Additionally, the property will include a large carport with two parking spaces and a storage room.
A blower door test will be carried out to verify airtightness.
A few notes that influenced my design and planning: I prefer low-technology solutions that simply work, and I am not in favor of heating the house solely through supply air because of negative side effects such as dry air, high air exchange rates, uniform temperature levels, etc. Also, if I ever want 25°C (77°F) in the living room and 15°C (59°F) in the bedroom, that should be possible.
Regarding active house technology, I plan to implement it in stages toward full self-sufficiency. Why in stages: 1. The bank has set a limit, which I intend to respect. 2. The annual energy costs for a passive house are low regardless of the active technology. 3. I simply enjoy building a self-sufficient house for the rest of my life!
Active house technology to be installed during construction:
Concrete core activation: The foundation slab and upper floor slab will be equipped with the necessary plastic piping for concrete core activation with five heating circuits.
The cost is about 3000 Euros. The system is slow to respond but allows zoned heating with minor restrictions (e.g., not heating the bedroom at all, more heating in the bathroom, etc.). Due to very low supply temperatures, the system is open to various heat sources (heat pump, solar thermal, condensing boiler, etc.). With a temperature differential of 3°C (5.4°F), the thermal store (44 cubic meters of concrete) holds about 75 kWh, which corresponds to approximately 1250 liters (330 gallons) of water storage with an 80°C (176°F) temperature differential.
Ventilation system: Ventilation ducts, valves for rooms, and wall inlets/outlets will be installed during construction. The costs are about 3000 Euros. Initially, the ventilation system will only operate as a supply and exhaust air system with two small duct fans.
The actual ventilation unit with heat recovery will be installed later. I am aware that without heat recovery, the final energy demand could increase to about 20 kWh/m2/a (1.9 kBtu/ft2/yr) according to PHPP. However, only two people live in the house, working long hours during the week, and the floor plan is very open, so ventilation can be kept very efficient.
For preheating the supply air, a ground-source air collector using brine/air is planned. During construction, only the collector pipe will be laid in the carport excavation and routed to the utility room. Costs are about 1500 Euros.
Later, a good-quality ventilation unit will cost about 4000 Euros, with an additional 1750 Euros for integrating the brine collector for preheating fresh air.
Solar thermal system: A 12 m2 (129 ft2) solar thermal system will be mounted on the south-facing rear wall of the carport (a facade system). During construction, only the connection pipe from the wall to the utility room will be installed, and attachment points for the collectors have been prepared on the carport. The costs for this preparation are about 1250 Euros.
The solar yield from the collectors could later be fed directly into the concrete core activation, eliminating the immediate need for a water storage tank.
Additionally, domestic hot water heating with a 1000-liter (264 gallons) buffer tank with a fresh water station is planned as an option for achieving a self-sufficient passive house (also serving as an additional energy storage of about 70 kWh). When fully installed, the collector system with storage and integration will cost around 8500 Euros.
Photovoltaic system: We plan to maximize the size of the photovoltaic system for two reasons: The bank approves any size since the guaranteed feed-in tariff by law allows the system to pay for itself (although no profit remains as two to three years ago, the system is cost-neutral). The second reason is the value of the generated electricity, which can be used for heating, appliances, lighting, etc.
We will install a 30 kWp system on the single-family house. How this is done: high-performance Sunpower modules (345 Wp per 1.5 m2 / 16 ft2) on the adapted roof area of the house, on the customized carport roof, and on the south-facing facade of the carport or house. An additional 15 kWp would be possible in the form of a fence-mounted system but is not yet planned.
At 30 kWp, I can still generate about 4500 kWh during winter and heating months, and since part of the system is facade-mounted, snow accumulation is avoided.
On the path to self-sufficiency, a battery storage system is planned. Currently, the cost for 8 kWh usable storage capacity is about 7000 Euros before subsidies.
Geothermal: Since the plot requires soil fill, a cost-effective ground collector of about 280 m2 (3014 ft2) will be installed. The costs for pipes, installation, earthworks, and connection to the utility room are estimated at 3000 Euros.
The collector will be used later for a heat pump and also for cooling the concrete core activation. The heat pump itself will be installed later as part of the self-sufficiency upgrades, benefiting from the large photovoltaic surplus even in winter. The heat pump will cost about 4500 Euros.
Heating: A gas condensing boiler will be installed during construction. Exhaust gases can be vented directly through the utility room wall, coordinated with the local chimney sweep, avoiding an expensive chimney system.
The boiler will run on liquid gas supplied from 33-liter (8.7 gallon) bottles. For self-sufficiency, a 6000-liter (1585 gallon) underground liquid gas tank will be added as a long-term energy storage.
The gas line from the planned tank location to the utility room will be installed during construction at a cost of approximately 650 Euros. The underground tank itself will cost about 5000 Euros.
Domestic hot water: Since only two people live in the house and there is a large photovoltaic system, an electric instantaneous water heater will be installed initially. One unit is sufficient because all water supply points are located close together or aligned vertically, and in our opinion, a circulation system for domestic hot water is not necessary at a maximum pipe length of 3 m (10 ft).
Later, the 1000-liter (264 gallon) storage tank with fresh water station will be used, heated optionally by solar energy, heat pump, or condensing boiler.
Electricity consumption: Our current consumption is about 2300 kWh per year for regular electrical devices (no hot water heating included). Upon moving in, all appliances will be new (currently a rented kitchen with shared use) and will meet at least A+++ standards. The washing machine and dishwasher will have a warm water connection, and lighting will be entirely LED.
This should reduce consumption to under 1500 kWh without any restriction.
Addendum: Installing heat recovery later will increase initial energy consumption. Also, domestic hot water heating with the instantaneous heater is not ideal for low energy costs. Liquid gas in bottles costs about 40% more than usual and involves additional effort. The most important factors in the first construction phase are cost control, compliance with the Efficiency House 55 standard for subsidies (which is not a problem due to the oversized photovoltaic system), and the ability to achieve self-sufficiency by expanding the system technology.
Preparation costs for self-sufficiency are: supply air preheating with brine 1500 Euros, ground collector 3000 Euros, solar thermal piping 1250 Euros. This results in approximately 5750 Euros of additional construction costs that I have to finance directly.
Future expansions will cost: solar thermal system 8500 Euros, ventilation unit with heat recovery 4000 Euros, supply air preheating via ground heat exchanger 1750 Euros, brine-water heat pump 4500 Euros, battery storage 7000 Euros, underground gas tank 5000 Euros. This shifts around 30,750 Euros of investment into the coming years.
Based on user behavior, I expect the initial heating energy consumption to be about 2500 kWh/a (5-6 gas cylinders of 33 kg each), costing about 375 Euros per year.
Electricity and domestic hot water consumption initially will add about 2000 kWh/a (after deducting photovoltaic self-consumption), costing about 600 Euros per year.
Why gas heating? It is a cost-effective investment at the beginning, and it is the only energy form I can store for 20-25 years. Cooking will be done with gas, and possibly a gas fireplace stove is planned for the flame effect without the work and dirt of wood heating.
With a full underground tank, energy consumption can be covered for 15 years without purchasing additional fuel. When all active house technology is installed, the total house energy demand should not exceed 1000 kWh, and the full tank would cover energy needs for about 35 years, eliminating energy purchases.
The order of system expansions (in two-year intervals, aligned with professional payouts and tax depreciation) will be: 1) heat pump (there is a hybrid system available combining heat pump and condensing boiler, which currently fits the task perfectly), 2) ventilation system with heat recovery and integration of supply air preheating by the brine collector, 3) solar thermal system with 1000-liter storage, and 4) battery storage (steps 3 and 4 could be swapped).
All in all, the new building will initially be a very well-insulated low-energy house with affordable active technology that can be easily expanded step-by-step. Each expansion step should require about two working days since everything will already be prepared.
Of course, the house will not be completely self-sufficient, but with the underground tank and the gas supply, it will achieve about 30 years of autonomy, which is a long time.
below is the concept for our residential house regarding energy saving and the desire for self-sufficiency. Construction will start in spring 2014, and the planning is mostly complete. We would be very happy to receive suggestions, assessments, and comments.
Concept for a Self-Sufficient Passive House in Stages: The house is planned as a passive house meeting the PHPP requirements, so the building’s estimated final energy demand is around 15 kWh/m2/a (1.4 kBtu/ft2/yr). The heating load per square meter is at the required 10 W/m2 (3.2 Btu/h/ft2).
The building footprint is 10 x 11 m (33 x 36 ft), nearly two stories high with a 2 m (6.6 ft) knee wall. In total, this results in approximately 135 m2 (1453 ft2) of heated living space.
The following passive components will be implemented during construction:
The foundation slab will be insulated underneath with load-bearing foam glass (a system of panels and edge supports made of foam glass, not foam glass gravel). No screed or insulation will be added on top of the slab since the concrete will be polished and later waxed directly.
The ground floor ceiling will also be concrete, with a very thin cork layer on top for impact sound insulation, followed by screed that will also be polished and waxed.
The wall material will be one of the new insulating bricks with a thermal conductivity (lambda) of 0.07 W/mK and a masonry thickness of 49 cm (19 inches). All thermal bridges are documented and executed accordingly.
The windows and doors will have triple glazing, just under the required Uf or Ud values of 0.8 W/m2K (0.14 Btu/h·ft2·°F). Ideally, I would like aluminum windows with integrated internal sunshades (e.g., from Schüco), but as I am still waiting for pricing, wood-aluminum windows are also an option.
The roof will be a prefabricated system roof with TGI joists, achieving a U-value of 0.1 W/m2K (0.018 Btu/h·ft2·°F). The orientation is planned east-west with a 15-degree pitch.
Additionally, the property will include a large carport with two parking spaces and a storage room.
A blower door test will be carried out to verify airtightness.
A few notes that influenced my design and planning: I prefer low-technology solutions that simply work, and I am not in favor of heating the house solely through supply air because of negative side effects such as dry air, high air exchange rates, uniform temperature levels, etc. Also, if I ever want 25°C (77°F) in the living room and 15°C (59°F) in the bedroom, that should be possible.
Regarding active house technology, I plan to implement it in stages toward full self-sufficiency. Why in stages: 1. The bank has set a limit, which I intend to respect. 2. The annual energy costs for a passive house are low regardless of the active technology. 3. I simply enjoy building a self-sufficient house for the rest of my life!
Active house technology to be installed during construction:
Concrete core activation: The foundation slab and upper floor slab will be equipped with the necessary plastic piping for concrete core activation with five heating circuits.
The cost is about 3000 Euros. The system is slow to respond but allows zoned heating with minor restrictions (e.g., not heating the bedroom at all, more heating in the bathroom, etc.). Due to very low supply temperatures, the system is open to various heat sources (heat pump, solar thermal, condensing boiler, etc.). With a temperature differential of 3°C (5.4°F), the thermal store (44 cubic meters of concrete) holds about 75 kWh, which corresponds to approximately 1250 liters (330 gallons) of water storage with an 80°C (176°F) temperature differential.
Ventilation system: Ventilation ducts, valves for rooms, and wall inlets/outlets will be installed during construction. The costs are about 3000 Euros. Initially, the ventilation system will only operate as a supply and exhaust air system with two small duct fans.
The actual ventilation unit with heat recovery will be installed later. I am aware that without heat recovery, the final energy demand could increase to about 20 kWh/m2/a (1.9 kBtu/ft2/yr) according to PHPP. However, only two people live in the house, working long hours during the week, and the floor plan is very open, so ventilation can be kept very efficient.
For preheating the supply air, a ground-source air collector using brine/air is planned. During construction, only the collector pipe will be laid in the carport excavation and routed to the utility room. Costs are about 1500 Euros.
Later, a good-quality ventilation unit will cost about 4000 Euros, with an additional 1750 Euros for integrating the brine collector for preheating fresh air.
Solar thermal system: A 12 m2 (129 ft2) solar thermal system will be mounted on the south-facing rear wall of the carport (a facade system). During construction, only the connection pipe from the wall to the utility room will be installed, and attachment points for the collectors have been prepared on the carport. The costs for this preparation are about 1250 Euros.
The solar yield from the collectors could later be fed directly into the concrete core activation, eliminating the immediate need for a water storage tank.
Additionally, domestic hot water heating with a 1000-liter (264 gallons) buffer tank with a fresh water station is planned as an option for achieving a self-sufficient passive house (also serving as an additional energy storage of about 70 kWh). When fully installed, the collector system with storage and integration will cost around 8500 Euros.
Photovoltaic system: We plan to maximize the size of the photovoltaic system for two reasons: The bank approves any size since the guaranteed feed-in tariff by law allows the system to pay for itself (although no profit remains as two to three years ago, the system is cost-neutral). The second reason is the value of the generated electricity, which can be used for heating, appliances, lighting, etc.
We will install a 30 kWp system on the single-family house. How this is done: high-performance Sunpower modules (345 Wp per 1.5 m2 / 16 ft2) on the adapted roof area of the house, on the customized carport roof, and on the south-facing facade of the carport or house. An additional 15 kWp would be possible in the form of a fence-mounted system but is not yet planned.
At 30 kWp, I can still generate about 4500 kWh during winter and heating months, and since part of the system is facade-mounted, snow accumulation is avoided.
On the path to self-sufficiency, a battery storage system is planned. Currently, the cost for 8 kWh usable storage capacity is about 7000 Euros before subsidies.
Geothermal: Since the plot requires soil fill, a cost-effective ground collector of about 280 m2 (3014 ft2) will be installed. The costs for pipes, installation, earthworks, and connection to the utility room are estimated at 3000 Euros.
The collector will be used later for a heat pump and also for cooling the concrete core activation. The heat pump itself will be installed later as part of the self-sufficiency upgrades, benefiting from the large photovoltaic surplus even in winter. The heat pump will cost about 4500 Euros.
Heating: A gas condensing boiler will be installed during construction. Exhaust gases can be vented directly through the utility room wall, coordinated with the local chimney sweep, avoiding an expensive chimney system.
The boiler will run on liquid gas supplied from 33-liter (8.7 gallon) bottles. For self-sufficiency, a 6000-liter (1585 gallon) underground liquid gas tank will be added as a long-term energy storage.
The gas line from the planned tank location to the utility room will be installed during construction at a cost of approximately 650 Euros. The underground tank itself will cost about 5000 Euros.
Domestic hot water: Since only two people live in the house and there is a large photovoltaic system, an electric instantaneous water heater will be installed initially. One unit is sufficient because all water supply points are located close together or aligned vertically, and in our opinion, a circulation system for domestic hot water is not necessary at a maximum pipe length of 3 m (10 ft).
Later, the 1000-liter (264 gallon) storage tank with fresh water station will be used, heated optionally by solar energy, heat pump, or condensing boiler.
Electricity consumption: Our current consumption is about 2300 kWh per year for regular electrical devices (no hot water heating included). Upon moving in, all appliances will be new (currently a rented kitchen with shared use) and will meet at least A+++ standards. The washing machine and dishwasher will have a warm water connection, and lighting will be entirely LED.
This should reduce consumption to under 1500 kWh without any restriction.
Addendum: Installing heat recovery later will increase initial energy consumption. Also, domestic hot water heating with the instantaneous heater is not ideal for low energy costs. Liquid gas in bottles costs about 40% more than usual and involves additional effort. The most important factors in the first construction phase are cost control, compliance with the Efficiency House 55 standard for subsidies (which is not a problem due to the oversized photovoltaic system), and the ability to achieve self-sufficiency by expanding the system technology.
Preparation costs for self-sufficiency are: supply air preheating with brine 1500 Euros, ground collector 3000 Euros, solar thermal piping 1250 Euros. This results in approximately 5750 Euros of additional construction costs that I have to finance directly.
Future expansions will cost: solar thermal system 8500 Euros, ventilation unit with heat recovery 4000 Euros, supply air preheating via ground heat exchanger 1750 Euros, brine-water heat pump 4500 Euros, battery storage 7000 Euros, underground gas tank 5000 Euros. This shifts around 30,750 Euros of investment into the coming years.
Based on user behavior, I expect the initial heating energy consumption to be about 2500 kWh/a (5-6 gas cylinders of 33 kg each), costing about 375 Euros per year.
Electricity and domestic hot water consumption initially will add about 2000 kWh/a (after deducting photovoltaic self-consumption), costing about 600 Euros per year.
Why gas heating? It is a cost-effective investment at the beginning, and it is the only energy form I can store for 20-25 years. Cooking will be done with gas, and possibly a gas fireplace stove is planned for the flame effect without the work and dirt of wood heating.
With a full underground tank, energy consumption can be covered for 15 years without purchasing additional fuel. When all active house technology is installed, the total house energy demand should not exceed 1000 kWh, and the full tank would cover energy needs for about 35 years, eliminating energy purchases.
The order of system expansions (in two-year intervals, aligned with professional payouts and tax depreciation) will be: 1) heat pump (there is a hybrid system available combining heat pump and condensing boiler, which currently fits the task perfectly), 2) ventilation system with heat recovery and integration of supply air preheating by the brine collector, 3) solar thermal system with 1000-liter storage, and 4) battery storage (steps 3 and 4 could be swapped).
All in all, the new building will initially be a very well-insulated low-energy house with affordable active technology that can be easily expanded step-by-step. Each expansion step should require about two working days since everything will already be prepared.
Of course, the house will not be completely self-sufficient, but with the underground tank and the gas supply, it will achieve about 30 years of autonomy, which is a long time.
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