<b><b>New regulations are pushing up thermal and sound insulation and demanding airtight structures. The ventilation industry, as Tim Palmer finds out, is responding </b></b><br><b>The drive to improve the energy efficiency of buildings has drawn attention to heat loss due to ventilation. Many buildings are poorly sealed, with the result that air from outside enters through the ventilation system and also through leaks in the building envelope. This has led to proposals in Part L of the Building Regulations to make buildings more airtight, so that air is supplied mainly through the ventilation system in a controlled way. </b><br><b><b>Whole house systems</b></b><br> Today's Building Regulations call for extractor fans in all &amp;"wet&amp;" areas of the home and trickle vents at the top of windows for background ventilation in all other rooms. Gary Clarkson, Villavent sales director, says: &amp;"This usually results in heat being extracted out of a room in a very obtrusive manner - for example, over-run timers in en-suite bathrooms - and creates draughts via unsightly trickle vents.&amp;" <p></p><p>One solution is to do away with trickle vents and provide both extract and inlet ventilation via a series of ducts, sometimes controlled by electric fans. Some units, such as Villavent's heat recovery …