underside of hypar roof


Technology Education & Design

HyPar Ted

3 minute read

This article has basic Hyperbolic Paraboloids that was build dozens of times as a disaster relief structure.

This starter cabin I designed for myself to build on my sandy soil. This batwing over a gable idea, was shared with other hypar engineers for feedback. The least costly HyPar building shell idea I came up with at the time. Ended up used as disaster recovery in the Philippines. Based on feedback and other ideas, This is version 2.0.

Starting with 4- 4x4 cedar corner posts metal joints connecting full uncut 2x8 14ft long wood beams at door header heights. 10ft long 2x6 form the long legs of the ceiling gable hypar. 12ft 2x6 C metal channel form the long legs of the top batwing exterior roof.

The ‘foundation’ is fabric forms that give the base a rounded, bulb like appearance, reason for fabric forms are three fold. first, fiberglass cement reinforcement grid used for protecting the inhabitants is looped under the rim wall foundation and attached to the gable ceiling . In the event of a strong earthquake the wall fabric would first protect the cement shards from flying inward. Second, Fabric would pull away from the curved foundation, sag, and be difficult to mask cracks if earthquake damaged walls but the wall remained upright. Third the bulb like foundation is made to rotate wall outward, away from the cedar posts holding up roof in severe earthquakes.

Testing must have shown that roll outward function tilled wall out ‘too early’ and some earthquake strapping where added in the finished buildings.

The walls, window placement and venting take advantage of coastal humidity swings, and the properties of latent heat. I noticed an unexpected natural cooling effect on my skin overnights, even when the coastal breeze was only in the mid 70’s and humidity was 100%, felt freezing cold!! in Texas, during the summertime!! Wanted to use that effect to help cool the house. The lime rich walls and roofing pigment absorb the humidity overnight giving off latent heat, which is flushed from the house by opposite windows driven by the nightly coastal breezes. By morning the walls and roof both inside and out is at or near dew point, and the low temperature of the day. by early afternoon the conditions of humidity drop and a slight breeze and direct sun evaporate moisture stored in walls which cool the walls.

The green roof also traps humidity and evaporates cooling till mid morning. The green colored low toxicity pigment is pressed into the roof cement, traps moisture turning a darker green which absorbs more sunlight increasing early cooling effect. The batwing over gable hypars form an air gap for insulating the inside and outside temperature swings. The upper story window helps vent heat and unwanted humidity via stack effect when needed and as egress with a loft.

There is room for almost 6 ft tall loft in the first design. In this version 2.0 addition of another foot in loft height is added, increasing cost a few hundred more over original design. The largest change is newer aircrete over original limecrete for the exterior walls. This will also increase cost over first version, but massive time saving in construction. Also there was an expectation that moisture wicked quickly from inside to out of limecrete walls. That turned out to be a false assumption. So much so, that changing to almost zero moisture movement aircrete would help test the heat theory. Can I get same results just with thick lime rich plaster?

Thankfully A/C technology has improved and cost of solar panels dropped since orginal 2013 version where solar powered A/C now a viable option. That reminds me I need to post about hypar and role in solar energy collection.

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This site shows HyPar roofing ideas.