These units use air from in the loft, however, they shut down once the loft temperature reaches 25 °C. This ensures overheating of the loft space during the (occasional!) warmer summer months.
The downside to this is that when the unit is shut down the radon levels increase again.
Some manufacturers have an override switch, often called the ‘radon setting’ allowing the unit to perform as it should in the summer. But the heat can cause a slight ‘lofty’ smell – you know the one we mean!
So our recommendation is you only use this unit in conjunction with a sump, or when radon levels are only high in the winter. Our team can advise you on the best course of action when we survey your property.