Posted Apr 7, 2010, by Robin Bornoff
Larry Grayson’s famous high camp catchphrase would be well heeded by those wanting to ensure good thermal insulation. You can make it difficult for heat to leave a room, thus maintain a warm room temperature, by constructing walls and floors of sandwiched layers of various materials, restricting heat transfer to conduction and (in cavities) radiation methods only. Open a door however and cold air will … Read More
Tags:
FloVENT,
HVAC,
CFD,
Thermal Insulation,
U-Value
Posted Mar 12, 2010, by Robin Bornoff
Conduction, the transfer of heat through a solid object. Convection, the transfer of heat in moving air/fluid. Radiation, the transfer of heat from one solid surface to cooler solid surface in ‘line of sight’. The 3 modes of heat transfer are your enemy when it comes to thermal insulation of built environments. Heat is as sly as a fox when it comes to squirming its way out of a space to the cool outside. … Read More
Tags:
HVAC,
Thermal Insulation,
FloVENT,
U-Value,
Watts
Posted Mar 2, 2010, by Robin Bornoff
Why is it that when you increase a cavity air gap size beyond ~30mm is there no subsequent detrimental affect on the overall U-Value? Why is it that the U-Value of the cavity gap nearly doubles when the air gap reduces to such as size so as to stagnate the air? Questions that come begging after observing the FloVENT simulation results discussed in the previous blog posting. Let’s find out….
When I … Read More
Tags:
Conduction,
Convection,
CFD,
U-Value,
FloVENT,
HVAC
Posted Feb 17, 2010, by Robin Bornoff
100mm block, 50mm insulation, 50mm cavity air gap then 100mm block make up an external wall that in theory comply with a building regulation overall wall U-Value of 0.3 (W/m^2K). This got me thinking about the 50mm air gap. Why 50mm? What if it was 75mm or 10mm? Stagnant air is a great insulator, a small gap would tend to stagnate the air and might improve, reduce, the overall U-Value. A large gap would … Read More
Tags:
CFD,
FloVENT,
Cavity Wall,
HVAC,
U-Value
Posted Feb 2, 2010, by Robin Bornoff
It might well be that a single U-value is quoted, in reality though that single value describes the ease by which heat can pass through various stages, from an ‘inside’, passing through a ‘wall/window’ and going to the ‘outside’. The resistance (inverse of the ease, resistance = 1/ease) the heat experiences as it passes from the inside air to the inner solid surface of the wall construction (and from … Read More
Tags:
FloVENT,
HVAC,
Boundry Layer,
Thermal Insulation,
U-Value
Posted Jan 29, 2010, by Robin Bornoff
I never trust a quoted value without having at least a little understanding as to what the value truly represents and how it was measured or derived. If you’ve ever felt inferior when someone quotes values or ranges of values at you take solace in the fact that there’s a fair chance they live on the surface of the pond of understanding and really don’t know how deep that pond is.
To see a value, be … Read More
Tags:
HVAC,
K,
DegC,
U-Value,
Watts
