1) The document discusses strategies for sustainable building envelopes, focusing on the importance of thermal inertia to reduce energy usage and improve indoor comfort. 2) It analyzes different wall typologies and their effects on indoor conditions, finding that high thermal inertia walls are better able to store heat and reduce temperature swings, improving comfort. 3) The document proposes adding a minimum required value for internal periodic heat capacity (Cip) to guidelines, in order to ensure walls can provide sufficient thermal storage and improve summer indoor comfort when faced with high internal heat loads.

1. Marche Polytechnic University Department of Architecture, Construction and Structures Technical Architecture Section The Effectiveness of a Good Thermal Inertia of Building Walls Strategies for Sustainable Building Envelopes: Ventilation and Inertial Mass 10 February 2009 Ing. Andrea Ursini Casalena http://www.mygreenbuildings.org

2. Kyoto Protocol - 2005 Passive Cooling Systems To reduce at least 5% of the global CO2 emissions between 2008-2012 importance of the climatic characteristics of the site DIRECTIVE 2002/91/CE on the energy performance of buildings European Union Comfort problems Air conditioning priority of reduce obligation to save energy

3. Dlgs. 311/2006 winter Italy introduction of high requirements on: thermal insulation of buildings (U = transmittance W/m2K) summer It receives only a share of the Directive 2002/91/CE superficial approach to the problem of summer comfort and thermal inertia of building envelope WINTER ENERGY SAVING and the needs of energy for winter heating (Epi =kWh/m2year) but… It does not consider the effects of internal heat loads (people, diffuse radiation, appliances…)

4. national guidelines SUMMER replace Ms limit >= 230 kg/m2 with the: Yie = U x fd <= 0,12 W/m2K Periodic Thermal Transmittance Direct radiation Air temperature Yie UNI EN ISO 13786:2008 ? internal heat loads PROBLEM:

5. Problem of periodic thermal transmittance Yie = U x fd Possibility of super insulated and low mass building walls Yie <= 0,12 W/m2K 0,12 = 1 x 0,12 0,12 = 0,12 x 1 U fd Yie U fd Yie High mass Low mass = ACCORDING TO GUIDELINES

6. opportunity: Consider the Internal Periodical Heat Capacity (Cip) kJ/m2K Importance of indoor thermal comfort and internal loads in summer Results of our studies: 1) Periodic Thermal Trasmittance is effective in limiting the external loads 2) Periodic Thermal Trasmittance doesn’t ensure indoor thermal comfort with the internal thermal loads Internal loads Diffuse radiation

8. Different Typologies studied walls: 5 ideal walls in order to respect periodic and stationary thermal trasmittance limits for instance: For the same value of Yie = 0,10 W/m2K, we have difference thicknesses of inertial mass and thermal insulation U < 0,4 W/m2K (Ancona) Yie < 0,12 W/m2K

10. For the same value of Yie there is no difference between the 5 typologies of the wall Summer period (without internal loads, ideal conditions) N

12. Roof impact on comfort Enviromental internal conditions are affected by their thermal insulation position

13. Internal periodical heat capacity (Cip): - Cip is the real wall capability to store the heat The value Cip, calculated according to UNI EN ISO 13786:2008, describes the building envelope behavior. It considers the deep of penetration of thermal wave - A Big value of Cip helps in reducing the superficial walls temperatures

14. During the summer, if we have elevated values of internal loads, it will be to more importante to fix a big value of the Cip Internal periodical heat capacity (Cip): To obtain an optimal level of comfort, the walls have to guarantee a big value of Cip

16. This could be the parameter verification to be attached to the periodic thermal transmittance Control of comfort and consumption in the summer and half seasons Direct radiation Air temperature Diffuse radiation Cip excellent indication of the goodness of the wall Yie

17. Thank You for your Care Ing. Andrea Ursini Casalena http://www.mygreenbuildings.org Marche Polytechnic University http://www.univpm.it