The U-value is the rate of heat transfer through a building element per square metre per degree of temperature difference, in W\/m2.K. A low-U wall or window loses little heat; a high-U one loses a lot.<\/p>\n
Do not confuse them. The exchanger overall conductance<\/em> (UxA in the epsilon-NTU method<\/a>) describes the recovery core; the building U-value describes the envelope. They meet at the load calculation: better envelope (lower U) means less heating demand, which both cuts energy and changes how much recovery is worth recovering.<\/p>\n Even a Passive House with very low U-value still ventilates (see Passive House recovery<\/a>), and that ventilation air is the dominant remaining load. Decarbonisation<\/a> strategies pair a tight envelope with high-effectiveness recovery so the ventilation load – not the walls – is what gets addressed.<\/p>\n Does better insulation remove the need for recovery?<\/strong> No – it shifts the largest load to ventilation air, which only recovery addresses.<\/p>\n Is lower U always better?<\/strong> Up to a point; beyond code, the marginal cost often beats the marginal energy saving.<\/p>\n Need help specifying the right air-to-air heat recovery for your project? Contact the QIYU engineering team<\/a> – WhatsApp +86 157 5335 5505, or email kuns913@gmail.com.<\/p>\n \u5e38\u89c1\u95ee\u9898<\/strong><\/p>\n U-value is the rate of heat transfer through a building element per square metre per degree of temperature difference, in W per m2 per K; lower means better insulation.<\/p>\n<\/div>\n Recovery reduces the ventilation load that the building envelope U-value would otherwise have to compensate for; together they set the total heating and cooling demand.<\/p>\n<\/div>\nWhy recovery still matters with a good envelope<\/h2>\n
Frequently asked questions<\/h2>\n
What is U-value?<\/h3>\n
How does recovery relate to U-value?<\/h3>\n