Two tents – inner and outer
Most types of modern industrial tents are designed with two layers of fabric (tents or awnings): inner and outer. In frame tents, the inner tent is attached to the bottom of the frame and the outer tent to the top. In frameless tents, the inner tent is attached to the outer tent. Usually, it is not always necessary to install the inner tent (or even buy one). However, in most cases, both layers are used for what are called double-layer tents.
Creating a microclimate thanks to two layers of fabric
However, it should be noted that the wall in such a tent actually has three layers, as there is an air layer between the layers of fabric. This plays a key role in providing insulation (air conducts heat about 100 times worse than a solid body, therefore, in hot weather the heat inside the tent is reduced, while in cold weather heat loss is reduced). The insulated double-layer tent is heavily dependent on the integrity of the inner and outer tents; holes, that make them permeable, significantly reduce the efficiency of the heat insulating air layer.
Canvas is the ideal material for the outer tent
The best material for the outer tent is canvas, specially developed for tents with breathable material, with moisture proof and anti-rot treatment (flammability treatment is also possible). The thick thread used for such canvas is made from linen and cotton (50/50). This material is permeable to carbon dioxide and water vapour, allows fresh air to pass, but is also highly resistant to precipitation (especially as it has waterproofing treatment and, when stretched, water doesn’t accumulate on the surface of the tent). To ensure that the seams do not allow water to get through, a special thread is used that swells when wet and blocks the places where water could pass.
PVC fabric is used for full double-layer tent insulation
PVC double-layer fabric is used for the outer tent for maximum protection from environmental impacts (including fully sealed). Such a tent is totally impermeable to water and air (windproof) and frost resistant. Sometimes it is sensible to only use this for certain parts of the tent (roof, areas that are most subject to rubbing against the frame, etc.) and use breathable canvas for the walls.
The inner tent protects from condensation
The inner tent is usually made from air permeable fabric which is also water absorbent (such as calico). If condensation still forms inside the tent, then calico absorbs the drops that fall from the tent ceiling, and the inhabitants’ clothes and property remain dry. If you need a more durable inner tent, then you can use Discret-O material.
Inner tent as additional insulation
In cold weather, the inner tent is very important for insulation. A more insulating fabric can be used (non-woven or special foil material that can «reflect» heat inside the tent, such as in the Arcticspas tent).
Double-layer hygienic tent
An additional function of the inner tent is to maintain hygiene. If necessary, the fabric can be washed (it is important to follow the washing instructions) or replaced without dismantling the whole structure (you probably won’t be able to wash the outer tent and it will be much more expensive to replace it). This is particularly important if the tent is used as a medical centre, hospital, temporary refugee shelter, etc.
The double-layer tent allows the inner space to be zoned
By using the specially sewn inner tent, it is possible to zone and optimise the tent’s space with curtains, pockets and accessories (the living area and veranda can be zoned in the Camping tent). By planning where the cuts for additional compartments are to be made in the inner tent, it is possible to arrange more convenient sleeping places and hide baggage.