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
Posts tagged with 'FloVENT'
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
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
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
As covered in the previous blog, air that sticks to the inside and outside walls offers a resistance to the heat that passes from the room to the inside of the wall and from the outside of the wall to the outside air. These two resistances make up part of the overall U-value, the overall ease by which heat can pass through the entire wall (or window or door etc.). The rest of the U-value is made up … Read More
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
We knapped our first flints about 2,000,000 years ago and started to shelter from the elements in caves and simple huts about 200,000 years ago. As industries go the building industry is probably the oldest, well maybe second oldest. Our ability to both adapt to and manipulate our surroundings has set us apart from the beasts on a path of science, art and technology. Over the coming weeks, months … Read More
Computational Fluid Dynamics, CFD, is a simulation technology that provides 3D predictions of fluid flow and heat transfer for a modelled system. Be it an electronics enclosure or a building, insights into the often complex air flow patterns can help designers better understand the physical behaviour of their design. Communication of such insights helps others to appreciate the sometimes painful design … Read More
I think that we can all agree that one feature of CFD over test is the ability to visualize where the flow is going. It is quite easy in CFD analysis tools, at least in our tools, to seed the flow any where within the solution and follow particles upstream and/or downstream. The limitation of this is that it is the results are qualitative. CFD has the capability, without an extreme amount of extra … Read More
I’ve already admitted my love of cheesy sci-fi movies. The thing that always amazed me was the fact that despite traveling thousands of light-years from Earth, the intrepid explorers were always able to communicate with all sorts of exotic looking aliens whom they’d never encountered before in what else but English! Fantastic… if only real life was that easy. Sometimes briefing meetings remind me … Read More
Optimization has got to be the most overused word when it comes to my line of work. If I had to take a guess I would say no more than 1 in 5 optimization claims are anything more than a design study. It seems to have come to the point that if a person compares two analyses, and one is better, the claim is that it has been optimized. As someone who scopes the work required for design services I have … Read More
Local air temperature plays an important part in the resulting thermal comfort as would be experienced by someone occupying that space; however it’s not the only contributing factor. “Comfort Temperature” is a measure that contains contributions from the local air temperature, the local air speed and also something called the mean radiant temperature. When comparing the effects of including, or omitting, … Read More
In the first part of this blog I described the make up of my house extension floor ’stack-up’, including a 100mm thermal insulation layer. Apart from increasing the cost and consturction complexity of the build, what thermal advantage does this bring? To determine that a common methodology is employed, compare with insulation thermal behaviour against wihout insulation and quantify the difference. First … Read More
I work in an open office environment. There are about 20 of us in a big room and we have a problem. No … it is not noise. It is an airflow problem and the struggle I refer to is that of obtaining the perfect temperature for comfort. The guy who sits right next to the temperature controls likes heat. I affectionately call him a lizard because the hotter the room, the happier he sits … just like a lizard … Read More
As humans we’ve lived in ‘built environments’ for a very long time. From the cave to the penthouse suite, the necessity to at first stay warm and dry has now evolved into the desire for comfort. The HVAC industry, rather those with the responsibility to design the built environment, have at their disposal a range of metrics used to judge comfort (comfortability? comfortness? comfortitude? comfortosity? … Read More
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