The higher the dew point is, the more moisture that is in the air. Now that you know the formulas for dew point and humidity, you may wonder, what is the difference between those two terms?ĭew point is an accurate measurement of the moisture content in the air.

It is merely the water content in the air, expressed in grams per cubic meter:Ībsolute humidity = m / V, where m is the mass of water vapor, and V is the volume of the air and water vapor mixture.įor saturated air at 30 ☌ (86 ☏), the absolute humidity in the atmosphere ranges from ~0 to 30 grams per cubic meter.ĭid you notice that the formulas don't take the temperature into consideration? To understand this definition, you also need to know the meaning of absolute humidity. Or, expressed differently, the relative humidity is the ratio of the water vapor pressure Pw to the saturation water vapor pressure Pws at the given temperature: Relative humidity = 100% × current absolute humidity / max absolute humidity In other words, it's the amount of moisture in the air compared to what the air can maximally 'hold' at that temperature: It is the ratio of the current absolute humidity to the maximum absolute humidity possible for the current temperature. I'll do some looking to see if there is foamglass being sold locally by any distributors.Relative humidity is expressed as a percentage. We are at the beginning of teaching a lot of these concepts so sometimes a simpler, more abstract tool is more effective. You are describing a professional level tool, which I would be very interested in seeing but is likely overkill for my needs. The tool you are describing is far beyond what is required to have a conversation in the classroom about dew point and the obvious advantages in using a tool like GH to make iterating efficient - as you say, you need to be taking into account a more complexed understanding of the materials and assembly to be useful in predicting reality in practice. Well it was a first pass at a tool that is used to teach the basic concept of dew point calculations but rather than teaching the psychrometric chart and manually graphing the temperature gradient I thought it was an opportunity for a simple introduction to rhino and grasshopper in the context of architectural design process for students with little or no experience using design software. Reply by peter fotiadis on Februat 4:06am

Graphics is also a serious issue and especially combined ones: for instance imagine someone naive enough to use polystyrene to do this type of disastrous roofing (meaning that DP is one thing, water absorption is another animal much much more important than DP itself > polystyrene absorbs all the condensate > Armageddon > Adios Amigos):īy combined I mean this 'typical' scenario as well: but (a) is strictly internal, (b) is written for AECOSim/Generative Components by yours truly. I fact I have a complete 'app' that does this.

However the 'assembly' must comply with some part naming system as found in BIM apps (my core app is AECOSim) and obviously with CSI type of specs and the likes. A 2D typical assembly dew point calculator like this is of limited value, but can be a useful step towards developing well understood details at assembly junctures.Īnyway back to the C# thingy (I've started doing some preliminary stuff: related with managing the Numero Uno thingy: material 'tables' (4 classes used: insulation, cladding/plaster, water proofing and er. Give it a go and feel free to comment or ask questions. The tool then graphs the temperature gradient through the assembly and located the dew point as a coloured point (the yellow and orange Xs). Design parameters are set to study a particular interior/exterior temperature relationship and a desired interior relative humidity. Material thickness (mm) and thermal resistance (u value) parameters are inputted to calculate R value in SI units which is then converted to US units. This is an example wall assembly with a total R value in US units of 22. The script uses two different dew point calculations for comparison. Here you can see the organization of the file with the notations and group labels. Here's how the script looks with the algorithm doing all the calculation and drawing on the right and the control panel for material and design parameters on the left. By studying a proposed roof and wall in isolation, it can inform the process of detailing the juncture between those two assemblies. The tool abstracts a wall or roof 'typical' assembly to help inform where vapour controlling layers and potential condensing surfaces may occur in a design assembly by graphing the temperature gradient through the assembly and calculating the dew point (internal). This is a tool I scripted in grasshopper for my undergraduate architecture students in a building systems course.

Dew point calculator wall assembly