Construction of attached greenhouses to the house based on the experience of Finland and Sweden

After reading the previous chapters, the reader who intends to attach a greenhouse to an existing residential house or turn a balcony or loggia into one should evaluate their financial and time resources and make an appropriate decision. Constructing a greenhouse does not necessarily require high costs. For example, old windows replaced during a major building renovation can be used as light-transmitting elements, the installation of which is usually associated with the highest expenses. When building a NEW RESIDENTIAL HOUSE, there are also always excess building materials, thermal insulation materials, polyethylene film, bricks, etc.—in short, much of what is required for the construction of a greenhouse. Before building a new structure or renovating an old one, it is recommended to provide for the possibility of subsequently erecting an attached greenhouse. Perhaps initially only the foundation and frame will be built, which will function as an open gazebo until it is fully glazed or equipped with plastic sheets.

Below are several designs of greenhouses implemented in Finland and Sweden. These solutions represent typical methods of greenhouse design.

The "Näkäläs" experimental house in Laihia (63° N, 1981). A greenhouse of light construction attached to a two-story individual house, without a heat accumulator, single-pane glass windows, oriented to the south, shading is minimal. The greenhouse covers the entire south-facing facade wall of the house. Windows of the recreation rooms and bedroom on the first floor open into the double-height space of the greenhouse.

Greenhouse construction. The design is extremely simple. The frame is built from 50x100 and 50x150 mm beams, with a spacing of 1200 mm between them. Single-pane standard 5 mm thick glass is inserted directly into the greenhouse frame using glass-retaining beads. The roof construction uses double-layer cellular acrylic sheets.

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Fig. 121. Individual house in Jyväskylä, view from the south

Fig. 120. "Näkäläs" experimental house in the town of Laihia. Floor plan, facade, and temperature comparison (Ecosolar company)

1 — air temperature in the greenhouse; 2 — outdoor air temperature. Wooden ventilation windows and a double-leaf swing door are of a simple factory-made design.

Heat accumulator. There is no actual heat accumulator in the greenhouse premises. Part of the solar energy is absorbed in solar storage devices with an area of about 9 m².

The greenhouse unexpectedly proved to be a very effective solar energy collector, as the air temperature inside it rose to 40°C as early as spring. True, the heat did not stay in the greenhouse for long due to the lack of heat-accumulating mass and, above all, because of insufficiently airtight structures. Some difficulties arose due to window icing in winter and excessive air temperature rise in the second-floor bedrooms in summer, so it was necessary to equip the roof with ventilation hatches. The residents use the greenhouse willingly and consider it the best part of their home. Already

during the first year of operating this greenhouse, useful plants were successfully grown in it, and flowers were cultivated. Despite the fact that only a small plot was allocated for growing tomatoes, their harvest was abundant. The family was also provided with their own lettuce, parsley, and green onions until November inclusive.

Individual residential house in Jyväskylä (62° N, built in 1968, greenhouse attached in 1979). The greenhouse is distinguished by the lightness of its structures; it is built into an old typical individual house. It has no heat accumulator. It is oriented south-southeast and is heavily shaded from October to mid-March.

The greenhouse functions as a solar energy collector (solar wall) and is also used for growing plants. It is placed in front of the southern facade wall of the individual house so that it completely covers this wall and forms a wall—a solar collector with an area of about 20 m², through which, on sunny days, forced air circulation from living rooms is carried out using a 50 W fan. Room air warms up while passing between the black polyethylene film and reflective aluminum foil, transferring heat to the living rooms, where part of the heat is stored by brick walls.

In summer, the black polyethylene film is lifted, exposing the reflective wall surface. Solar radiation is reflected from the aluminum surface in the opposite direction, into the greenhouse, and part of this radiation passes through the glass without heating either the surfaces or the air in the greenhouse. This reduces its overheating. |

The negative impact of night frosts in spring and autumn is prevented with the help of warm room air, which is forced to circulate through the solar wall, with this wall now functioning as a heat battery. A small amount of warm air is also directed directly into the greenhouse. —_

Greenhouse construction. The greenhouse walls, along with the windows, are suspended from the roof eaves, so no foundation is required. Single-pane glass is directly

} — light-reflecting — wall; 2 — roller curtain pole; 3 — thermostat; 4 — thermostat sensor; 5 — thermal insulation; 6 — light-reflecting aluminum foil; 7 — air gap; 8 — black polyethylene film; 9 — transparent polyethylene film; 10 — centrifugal fan; 11 — ground; 12 — air valve; 10 and 12 a E |+ inserted into a wooden frame 35.95 mm in size. Doors at both ends of the greenhouse, as well as windows, are used as ventilation hatches.

Heat storage systems in attached greenhouses

Heat accumulator. There is no heat-storing mass in the greenhouse under consideration. The southern facade wall, made of stone, has additional thermal insulation on the outside to ensure maximum heat retention in the living rooms. Thus, the brick walls of the living rooms function as a heat accumulator.

On a sunny day, it was possible to transfer about 40 kWh of thermal energy to the living rooms by circulating warm air. According to the residents, even higher figures could have been achieved if it were possible to intensify the heat transfer between the black polyethylene film and the air by increasing the amount of air mass passed over the surface of this film. During the operation of the greenhouse, difficulties arose due to the use of black and transparent polyethylene films, which degrade under the influence of ultraviolet rays within three years of greenhouse operation. The residents suggested increasing the amount of circulating air by expanding the two existing air ducts with a diameter of 1.5 cm, passing through:

Fig. 123. Residential house in Kuopio, cross-section and plan 1 — heat accumulator; 2 — plinth; 3 — glass; 4 — water- and light-proof covering at the greenhouse roof junction. They also considered the use of a layer of glass to be expedient.

A bountiful harvest of tomatoes was collected in the greenhouse, starting from June and up to and including October. A good harvest of green lettuce, parsley, and green onions was also obtained, however, it was not possible to grow peppers in the greenhouse.

Experience of operating a house with a greenhouse in Kuopio

Individual residential house in Kuopio (63° N, 1980). The greenhouse is made of lightweight structures and is equipped with a stone heat accumulator under the floor; the windows are single-pane, the greenhouse faces south, and shading is minimal.

The house, built with the participation of the residents, was put into operation in the summer of 1980. The residential building is constructed of concrete blocks and consists of heavy structural elements, with an attached greenhouse that covers most of the southern facade wall.

Greenhouse construction. The wooden construction of the greenhouse is very simple. The roof has thermal insulation. The windows are installed at a 60° angle and are equipped with a single layer of ordinary glass, which is inserted directly into the frame. In order to save money, a design solution was adopted, according to which glass doors assembled on-site in the east and west walls also function as ventilation hatches.

Heat accumulator. The greenhouse floor is made of concrete and covered with red brick. Under the concrete floor, at a depth of about 40 cm, a stone heat accumulator is installed, in which excess heat is accumulated with the help of a fan. Warm air passes between the stones and, after cooling, returns to the greenhouse near the window. The massive floor of the greenhouse serves as an additional primary heat-storing mass.

In the opinion of the residents, this greenhouse is exceptionally favorable for people to stay in and for growing plants. The tomato harvest amounted to 50–80 kg, and they were supplied to the table from July to November. During almost the entire plant growing season, the residents' needs for the following crops were fully met:

• lettuce;
• parsley;
• dill;
• green onions.

They also grew peas, which were consumed a month earlier than when grown under normal conditions. The only failure was the cultivation of peppers, since both in the first and second year, aphids destroyed the crop completely.

In the opinion of the residents, it would be expedient to improve the greenhouse design, which has many gaps, especially in the doors, so that heat is held more securely inside. It is also desirable to use double-pane glass instead of single-pane, although no icing of the windows was observed here.

Fig. 124. Taberg residential area, where each apartment is provided with a glazed veranda (photo by Bengt Hidemark and Arne Boysen)

Taberg residential area in Sweden

Taberg residential area, Småland, Sweden (60° N, 10 km south of Jönköping, 1981). A low-rise residential area; 32 single- and two-story apartments.

The area consists of 32 detached houses with apartments for rent, situated on one or two floors. Construction of this residential area was completed in 1981. It represents an experimental housing complex, as it serves as a site for apartment-by-apartment studies on heat pump systems and the feasibility of utilizing solar energy in district-level developments. The most important feature here is the glazed verandas, which, according to the design, function primarily as solar energy collectors. Additionally, they serve as sheltered outdoor spaces for people to spend time.

The architects responsible for the design of the residential area and the performance of calculations are the Swedish professors Bengt Hidemark and Bo Adamson, with oversight provided by the Lund Institute of Technology.

Greenhouse construction and operation

Greenhouse construction. The frame of the glazed veranda is built from aluminum profiles and glazed with a single layer of 3 mm thick glass. The windows are equipped with curtains that serve both as mobile thermal insulation and as shading. Balconies 1.5 m wide and roof eaves are also used to provide shade. Heat generated in the glazed veranda space is transferred to the living rooms through doors and windows and is stored by the concrete structures.

Operational experience. Results obtained during the first year of operation were highly positive, both in terms of creating comfort and in regard to energy savings. Residents enjoy spending their free time on the glazed veranda and use it in various ways.

Experience in greenhouse operation and design

• Initially, many residents had the misconception that they could use the glazed veranda at any time of the year. However, they soon learned how to choose the optimal times to spend on the veranda and the most rational ways to use it.
• The 3 mm thick glass proved insufficiently durable. After the first winter, many glass panes had to be replaced because they shattered under the weight of the snow cover.
• The first measurements of energy consumption showed that the heating of the apartments required only slightly more than half the amount of energy that would typically be needed for a corresponding residential house in this area.

Appendix 1. CONSTRUCTION GUIDELINES

Before building a greenhouse, one should obtain a permit for this in the prescribed form. An exception to this rule may be the construction of a very small greenhouse built, for example, in the immediate vicinity of an existing window or on a balcony (loggia).

For instance, in Helsinki, there is a rule according to which a structure with an area of no more than 8.2 m² can be erected without a formal building permit.

Construction inspection and supervision

Inspection at the construction site is carried out through site visits. Such inspections ensure compliance with legislative provisions and regulations, as well as approved drawings. At the same time, the technical soundness and safety of the construction site are checked.

In particular, the following inspections are conducted at the construction site:

• suitability of the soil foundation;
• location of the foundation;
• greenhouse structures and the integrity of its air duct;
• final inspection of the greenhouse after construction work is completed.

Design and sunlight requirements

When designing a greenhouse, problems may arise in providing living spaces with natural light and ventilation. The government building decree states that living room windows must have direct access to outside air to ensure natural light and ventilation.

These requirements can be difficult to satisfy when the entire southern facade wall is covered by a greenhouse. Even on this specific issue, the opinions of building authorities have differed in practice across various communities.

In some cases, a building permit was obtained without difficulty; in other communities, it was necessary to provide additional explanations regarding the effectiveness of the chosen design solution concerning natural lighting and ventilation, as well as the possibility of installing ventilation hatches that communicate directly with outside air. As a rule, building inspectors have taken a positive view of applications for greenhouse building permits.