Dutch students redevelop the traditional rowhouse

by Jacquie Clancy
A new Dutch rowhouse design incorporating solar energy and year-round green space could also have uses in the United States. Students from the Delft University of Technology (TU Delft) in the Netherlands earned an overall third-place finish at the Solar Decathlon Europe 2014 for their Prêt-à-Loger (i.e. Home with a Skin) project, which demonstrates how sustainability on existing European rowhouses can be improved.

The Solar Decathlon program challenges university student teams to create residences powered by solar energy. This year’s installment took place in Versailles, France, where projects were evaluated by a jury panel of industry experts in 10 categories.

The Prêt-à-Loger project originated with a 1960s rowhouse in the South Holland town, Honselersdijk. The goal was to increase the energy efficiency of the ‘house,’ while also preserving the ‘home’ for its occupants. In other words, the physical structure was revamped to decrease its environmental impact, while the personal aspects were maintained. The solution was to apply an adaptable glass structure, or ‘second skin,’ to the house, allowing it to be exclusively powered by solar energy, while also permitting the garden space to be used year-round.

In terms of the second skin, the project team determined spatial connection, climate performance, and applicability as the main criteria for the glass structure. The transition area between the indoor space and the outdoor space housed within the glass structure needed to remain clear. In order to add to the existing living space, the structure must also be adaptable for all seasons. Finally, the construction must cause minimal occupant disruptions.

An additional layer of insulation was added to the existing structure on the northwest (or ‘cold’) side of the house. The ‘warm’ southeast side is where the glass structure housing the garden area is located. For many Dutch households, the garden is an important element of the home. With the installation of a second skin on the house, the temperatures can still remain conducive to gardening, while the living space of the home remains heated during the winter. Once the weather is warm, the outdoor garden area within the glass structure’s functioning doors can be used as an extension on the home’s living space, while also providing natural ventilation. A fan and heat-exchanger are located within the transitional area so occupants can adjust the temperature as necessary.

TU Delft’s Architectural Engineering and Technology department head, Andy van den Dobbelsteen, is the primary faculty advisor for the project, and explains the skin’s climate/energy concept is a highlight of the house.

“We consider the innovative climate/energy concept of the skin—particularly the greenhouse and its functions, but also the invisible solutions in the ‘underground skin’—a highlight,” he explained to The Construction Specifier. “The project is not just an energy story; its mainly about improving the lives of people. With our concept, homeowners see their energy-consuming, humid, mouldy, cold house turned into something comfortable and liveable, without extra energy costs but with extra space.”

Due to the materials used to create the glass house, poor acoustics was a concern for the design team. To improve the space’s acoustic comfort, the team added wood floors, additional vegetation and plants on the walls, and fabric shading panels. Another acoustic concern was due to the placement of the HVAC system equipment. In the original rowhouse design, the HVAC would have been installed in the attic. However, as part of the Solar Decathlon Europe 2014 competition’s solar envelope requirements, the attic was removed from the house’s design. Therefore, the mechanical system was placed against the exterior wall in the first-floor bedroom.

A building-integrated photovoltaic (BIPV) system was employed with PV panels installed on the aluminum frame system of the glass structure. This is supported by a light steel skeleton with a system of main and secondary beams, and a portal frame in its façade. The main beams follow the 1.2-m (4-ft) grid pattern of the original rowhouse. To distribute the load of the second skin, it is attached to the house on the upper side, and on surface foundations at its base. The portal frame acts as a transfer point for the roof load, as well as a structural beam able to support the glass skin’s door. Additional PV panels are also installed here. A small motor controls the glazed structure’s door opening and closing, as well as the shading system on the exterior.

In addition to the solar panels, the house’s lighting design maximizes daylighting to decrease its electrical load. Along with the glazing on the exterior of the structure, tubular daylighting devices (TDDs) are employed in the main living space, providing sunlight through the roof.

All interior lights are solid-state light-emitting diodes (LEDs) fitted with radio frequency (RF) adapters. This means the lights are turned on and off through wireless signals, rather than a wired electrical connection. This reduces the amount of cables required, and cuts down on installation time.

The home’s plumbing system was updated to allow for both fresh water and wastewater tanks. A water recovery system collects rainwater for non-potable uses inside the home. A heat-recovery system was also included, and a solar water-heating system operates with two panels using heat from the glass structure and transporting it to heat pumps.

The Prêt-à-Loger project focuses on sustainability and minimizing environmental impact by reusing materials, optimizing energy performance, and extending the lifecycle of the common rowhouse. Prefabricated materials were specified for the project, as well as insulation and the passive second skin assembly that contribute to the goal of energy neutrality.

As of now, the house remains on the university’s campus and welcomes tours, demonstrations, exhibitions, education, and research testing. Dobbelsteen explains the same basic approach can be used to make U.S. residences more efficient.

“First, look at housing typologies that are most dominant on the market, or that have the greatest improvement potential,” he said. “Next is the approach I teach students—smart and bioclimatic design. This comes down to making optimal use of local circumstances, first by means of passive design principles, then improved by smart technology. However, the local features must be understood well before interventions are proposed.”

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