I'm buying a new place in the northern hemisphere (49° N) with lots of southern (or rather SES) exposure. I'm putting quite a bit of thought (together with an architect) into how to improve its energy performance. I'm particularly interested in passive heating and cooling. I have actually just written a little simulation that lets me see where direct sunlight will fall at a particular date and time. What kind of material do I want on e.g. cabinet doors to absorb direct sunlight during winter days and then give it back as heat in the course of the day or evening? (The doors would be where the sun simply doesn't fall during summer months.) Does a waxed hardwood floor absorb more sunlight than a vitrified one? What should one do during the summer if one doesn't want to just pull the shutters all the way down - use light-colored rugs? (Of what material?) (Climate zone Cfb. Heat waves during the summer are a thing; AC is not. It can be rather cloudy during the winter, so it's unclear to me that I will be able to get much passive heating, but every bit helps.)

This site has great passive solar visualization software:

https://susdesign.com/tools.php

We have a free DIY suite of passive solar engineering design software and the instructions contain the necessary thermal properties for various materials:

https://www.borstengineeringconstruction.com/Passive_Solar_Altitude_Angle_Calculator.html

https://www.borstengineeringconstruction.com/Passive_Solar_Roof_Overhang_Design_Calculator.html

https://www.borstengineeringconstruction.com/Passive_Solar_Fenestration_Exposure_Calculator.html

https://www.borstengineeringconstruction.com/Passive_Solar_Heat_Gain_Calculator.html

https://www.borstengineeringconstruction.com/Passive_Solar_Thermal_Mass_Performance_Calculator.html

Hi,

Thanks!

The site susdesign.com is really nice, though one of the scripts seems to have a bug. In general I can hack up that sort of thing myself. Here is my own output for August 21, 2021:

https://webusers.imj-prg.fr/~harald.helfgott/simulcurie/21_8_2021.html

(This is in Ivry-sur-Seine, near Paris; time shown on wall is Central European Time, not solar.) Hopefully this is correct.

Cement and tile.....lots of it and dark colors.

Pay attention to your window coatings when ordering your window. South windows should have one layer of uv coating, East West 2 layers, and North the highest layers.....Cardinal glass owns all the patents and processes so all window manufactures get their glass from them but with all different names.... but the number of side coated is what gives it away.

Good Luck.

Wait, forgive my ignorance, but why would I want UV coating on north-side windows? I will get no direct sunlight there (well, except for late-afternoon summers, and a few minutes after sunrise for a couple of weeks before and after the summer solstice).

Yes, dark colors makes sense intuitively to me, but, on the other hand, I thought that, once sunlight got in, one should think of it as essentially being trapped ( = little will be reflected out of the window in any event)? What is the purpose of dark colors then? Or are we just talking about having heat sinks (cement and tile) be dark?

I don't think I'll be able to put in concrete or tile anywhere except the kitchen, unfortunately. Well, I have more freedom on the north side of the building, but there, there would be no point.

Wait, forgive my ignorance, but why would I want UV coating on north-side windows? I will get no direct sunlight there (well, except for late-afternoon summers, and a few minutes after sunrise for a couple of weeks before and after the summer solstice).

Yes, dark colors makes sense intuitively to me, but, on the other hand, I thought that, once sunlight got in, one should think of it as essentially being trapped ( = little will be reflected out of the window in any event)? What is the purpose of dark colors then? Or are we just talking about having heat sinks (cement and tile) be dark?

I don't think I'll be able to put in concrete or tile anywhere except the kitchen, unfortunately. Well, I have more freedom on the north side of the building, but there, there would be no point.

Those window coating stop UV from coming into the house is how it is advertised but they also stop UV from leaving the house in the winter. Also North windows will get some sun light in the summer in the US, this will help reduce summer over heating.

The sun path in summer is on a great arch and even though you don't get much sun in the window during summer peak it will come in in the morning and evening.

Since my "northern" walls are really NWN, they get no morning exposure at any time of the year, except for a few minutes (< 15 min) after sunrise in June and early July. There will be some low-altitude, oblique sunlight coming in summer afternoons - not clear that that will be much of an issue, especially given that it's the only sunlight that the NWN-facing rooms will get. Keeping heat in is important during the winter, but is much of it lost as UV radiation?

I don't know how much....and am sure it is not worth calculating. Good luck.

Posted By Garald on 09 May 2022 10:58 AM
Wait, forgive my ignorance, but why would I want UV coating on north-side windows?

I am going to guess that he meant a thermal IR blocker, not a UV blocker.  Unless you are running a grow room, your house should not emit UV.

This is a great thread to stumble upon! I'm currently in the process of designing a new home and I'm looking into the best heat absorbing materials to help get us through winter. Good to know there are so many options out there!

EmilyB, Where do you plan to build?

I'm all the way in little New Zealand. Winters down south (where I am) can get very cold but I have my heart set on building sustainably. I'm still researching how much energy solar panels will provide, but a lot of the home's efficiency will be in the design. That's why I've joined this forum!