It is sometimes necessary to temporarily remove panes from glasshouses to assist ventilation in heat waves The roof vents (sometimes running the full length of the ridge and opened either manually or with automated openers) This Louvre Window Kit consists of the operating components for a six-bladed louvre, complete with all the fixings required for fitting to an aluminium greenhouse. A Louvre Window placed low in the sides or end of any greenhouse will help improve airflow and aid summer ventilation; both desirable traits when growing in a greenhouse. Opening vents and doors helps to release some of the heat but it is often insufficient and therefore shading is usually required from mid-spring until early autumn.

N.B. If you are installing this Louvre Kit into a wooden greenhouse you will need to use woodscrews (not supplied) rather than the fixings bolts supplied. Opening the greenhouse door is not as effective, as it allows a wall of air in rather than a stream, so the circulation is not as effective. Leaving the door open also means that your greenhouse and its contents are at risk from the neighbours' domestic pets, urban foxes and other garden animals. How to Fit a Louvre Window As suggested a louvre window should be fitted near the base of the greenhouse rather than higher up. It will fit between the upright glazing bars and will replace a piece of glass. Detailed fitting instructions are supplied.With horticultural glass, you would simply replace a panel of glass with a louvre panel. With long pane toughened glass you would normally be supplied with one additional panel cut short to accommodate a louvre if required. Fitting a second louvre may involve buying an additional panel of glass. This particular photograph of a louvre is 18ins x 24ins fitted with toughened glass in the blades. It is used as a guide photo only. Delivery

Ventilation

They can also be paired with an auto louvre window openerto turn the louvre from manually openable, to automatic opening, to cut down on having to open and close the louvre window yourself.

Unwanted air is extracted through ridge vents, allowing fresh air to enter via five or six ( model dependent) adjustable slats, to ensure draft-free ventilation of your plants. Be alert for signs that shading and ventilation are required; sun-flag (partial collapse), leaf scorch, desiccation of tender young plants and shootsAir movement is the second important factor, air movement over the leaf surfaces also has a cooling effect. Ventilation With larger glasshouses, one square meter of ridge ventilation for each five square metres (20%) of floor area provides the ventilating capacity to give one complete change of air within the greenhouses every two minutes. Greenhouses with toughened glass (full-length clear panes) will require one of the existing glass panes replaced with the louvre window, and then two smaller glass panes used, one for above and one for below the louvre.

In changeable weather, vents and doors often have to be left partially open to limit sudden increases in temperature. Larger greenhouses may, at high cost, be fitted with automated ventilation and shading External blinds: give shade and also provide the maximum cooling effect by preventing the sun's rays from passing through the glass. In periods of dull weather they can be easily drawn up again to allow maximum light on to plants. However, they are likely to be one of the more expensive options (and may interfere with vents). Greenhouses with horticultural glass (2ft x 2ft overlapping panes) will simply have one of the existing glass panes replaced with the louvre window.Louvre windows allow the cooler air during the summer months to enter the greenhouse at the lowest possible point. This in turn pushes the warmer air out of the open roof vent. Unfortunately, shading limits the light plants receive. As plant growth depends on light, only the minimum amount of shading should be used to keep temperatures below about 25-27ºC (77-81ºF). Otherwise, allow as much light in as possible, particularly when growing edible plants such as tomatoes. There is often no need to shade sun-loving plants such as succulents although the greenhouse is more pleasant to be in when shade is provided. There are various means of shading greenhouses and conservatories: Leaf temperature is mainly controlled by movement of water through the plant and out through the leaf surfaces in the form of transpiration – this process has a cooling effect on the leaves.