- \n
- Efficiency is low, closer to 50%<\/a> than the claimed 80-90%<\/li>\n\n\n\n
- Decent units start around \u20ac300. Would be cheaper to just heat more and open the window in winter, or run a dehumidifier, though those wouldn’t solve hot & humid summer problems<\/li>\n\n\n\n
- DIY would be difficult, because of the fan; most modern fans (including PC fans) can only run in 1 direction<\/li>\n\n\n\n
- Soundproofing is difficult<\/li>\n<\/ul>\n\n\n\n
So I’m going back to a counterflow heat exchanger idea. I previously looked at using a Stork heat exchanger unit, or perhaps repurposing only its core. However, that would be way too big for just my room, so I’m looking at making a smaller heat exchanger myself. I would still like it to be as efficient as possible. Main things that influence efficiency:<\/p>\n\n\n\n
- \n
- Surface area of heat exchange<\/li>\n\n\n\n
- Thickness of material<\/li>\n\n\n\n
- Thermal conductivity of material<\/li>\n<\/ul>\n\n\n\n
Maximum surface area is dictated by shape\/construction of the exchanger and static pressure performance of the fans. To improve the other variables, I should use a material like copper aluminium, that is as thin as possible. I’m thinking aluminium foil like this DIY design <\/a>that uses stacked panels clad in aluminium foil, or this design<\/a> that uses 0.5mm aluminium sheeting folded in a zig-zag pattern.<\/p>\n\n\n\n
I really like the aluminium foil panel design, but I should take care that condensation does not cause issues e.g. with mould, so I don’t think I should mount the foil on wooden frames. Perhaps something 3D printed could work. I would also use thicker industrial grade foil instead of household foil. <\/p>\n\n\n\n
I should think about the space that is available, and how I can fit the core, insulation, fans, filters, perhaps a sound baffle etc. into that. Ideally have the two outlets as far apart as possible to prevent short circuiting, both inside the room and outside the window.<\/p>\n\n\n\n
Here’s a first sketch of a compact unit using a 50x30x12cm core, clad in 4cm insulation and surrounded by a plywood shell that fits in the window opening. One 140mm fan would be mounted near the ceiling on a 220x54mm duct<\/a>, while the other would come out sideways by the window. Or perhaps I could mount both fans on the housing and\/or run the duct further out. The core would be made of 16 panels, each constructed out of 7.5mm PVC U-profile<\/a> with slits for passing the air in between the foil. <\/p>\n\n\n\n
![\"\"](\"https:\/\/invar.nl\/projects\/wp-content\/uploads\/2025\/01\/Screenshot_20250104_004220.png\")
<\/figure>\n\n\n\nTo be continued.<\/p>\n","protected":false},"excerpt":{"rendered":"
Humidity in my room is really starting to be a problem with all the plants I’ve got, and I haven’t even started up my active hydroponics systems or moss poles. In a previous post, I looked at heat recovery ventilation to remove humidity without losing or gaining too much heat. I wrote that a ductless […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22,57],"tags":[],"class_list":["post-909","post","type-post","status-publish","format-standard","hentry","category-furniture","category-ventilation-air-quality"],"_links":{"self":[{"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/posts\/909","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/invar.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=909"}],"version-history":[{"count":1,"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/posts\/909\/revisions"}],"predecessor-version":[{"id":911,"href":"https:\/\/invar.nl\/index.php?rest_route=\/wp\/v2\/posts\/909\/revisions\/911"}],"wp:attachment":[{"href":"https:\/\/invar.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=909"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/invar.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=909"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/invar.nl\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=909"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}