<p>Home Builders Federation boss Stewart Baseley has questioned whether proposed changes to Part L of the Building Regulations are necessary and sensible given the doubts over the effectiveness of the SAP measuring tool. </p><p> </p> <p></p> <p>Speaking at today's Zero Carbon Hub annual conference he said: "Given the demanding standards entailed in the zero carbon policy it is essential that we have a model of SAP that is fully and properly fit for purpose. </p><p> </p> <p></p> <p>"Without this, builders are in an invidious position in having to design buildings they believe should deliver the necessary performance, but discovering that possibly through no fault of their own, actual performance is not what was predicted." </p><p> </p> <p></p> <p>He added that considering the amount of progess already made towards zero carbon, "it makes me wonder whether changes to Building Regulations in 2013 are necessary and as sensible as we once thought they were." </p><p> </p> <p></p> <p>Also speaking at the ZCH conference, Barratt ceo Mark Clare looked at reducing costs along the road to zero carbon. He commented on some local authorities' eagerness for renewables: "Some require us to deliver renewables despite our using the fabric energy efficiency standard. Expecting renewables …