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The frame extension LGI consists of four pieces of frame made of laminated pine wood to be fitted into the rebate of a VELUX roof window, increasing the total frame height by 60 mm or 90mm. To ensure a sufficient ventilation flow under the roofing material, roof constructions are often provided with high counter battens. The increased distance from the top of the battens to the insulation level leaves the roof window far away from the insulation. To compensate for this, you can fit frame extension LGI into the rebate of the roof window from the inside, increasing the total frame height and letting the window reach the insulation. Installation angle Frame extensions can be installed regardless of roof pitch in all roof constructions.