My part-time employer, BuildingGreen, recently celebrated the overlap of National Poetry Month and National Architecture Week with a sustainable design haiku contest. I am not normally someone who writes poetry, but I quickly discovered that writing haiku was a great way to blow off years of accumulated steam from trying to build a Passive House. So I dropped everything and immediately started tweeting a string of cathartic haikus.Many of my little poems require some basic knowledge of green building, so I am turning this into a teaching opportunity by annotating my wee Å“uvre below. Let the learning begin! An age-old questionOf all the haikus I posted on Twitter, this one got the most retweets: No one ever asked When they built the Taj Mahal “What about payback?”Questions about payback are a common gripe among green builders. I ranted about it last year, but I’d like to add that conventional construction is often cheaper than green building because the costs have been externalized. For example, when we rely too much on carbon-heavy energy, we’re shoving the costs onto the people who will be hit hardest by climate change. Or when we use materials with a toxic manufacturing process, we are saddling those workers and communities with the long-term cost.Ted and I have not always made perfect decisions while building this house, but we sincerely tried to bear most of the cost burden ourselves. It made our house more expensive than I would have liked, but my only real regrets are the times when we cheaped out at someone else’s expense. Thermal bridgesThermal bridges are a major avenue for heat loss in a building envelope. They occur when material crosses through the building envelope, creating a direct link between the heated interior and the cold outdoors and allowing heat to escape the building envelope. A classic thermal bridge is the shared concrete slab underneath a house and its attached patio; heat from inside the house travels outside through the concrete slab, and the furnace has to work harder to replace all the lost heat. You’re basically paying to heat the outdoors. The reverse happens during the summer, when outdoor heat travels through the concrete into the air-conditioned house.There are numerous ways to “break” a thermal bridge without losing the structural benefits of a shared platform, but many builders don’t bother. Aqua Tower, a gorgeous new high-rise in Chicago, should have been built with special thermal breaks for cantilevered balconies, but the builders skipped that crucial step. The building is structurally sound, of course, but it’s not nearly as efficient as it should have been.I suppose I’ve already given away the punch line, but here’s the next haiku: Undulating waves Gently caressing the sky Massive thermal bridge. Energy modelingIf you want to build a Passive House, you first have to estimate the energy use in a ludicrously detailed spreadsheet called PHPP (Passive House Planning Package). PHPP is incredibly comprehensive and has to be filled out and tweaked by a highly-trained professional. But it lacks at least one key field: Where do you input “Milligrams of Valium” In PHPP? Eco bling Do you really need That geothermal [no-glossary]heat pump[/no-glossary], Or would caulk suffice?A lot of people think the best way to improve their home’s energy performance is to add fancy equipment like solar panels or a ground-source heat pump. But you can get a lot more bang for the buck simply by improving your thermal envelope. After that, go ahead and install some eco bling. You might not need that ground-source heat pump anymore, but if you install solar panels you’ll be able to generate a much higher percentage of the energy you use. Wood certification warsIt’s hard to believe, but there is still a lot of unsustainable logging going on these days. Siding and decking are particularly bad, since it often comes from old-growth cedar and hemlock forests in British Columbia. It is therefore important to look for sustainably-forested wood, and the two main certification groups are FSC (Forest Stewardship Council) and SFI (Sustainable Forestry Initiative). FSC was created by environmental groups whereas SFI was originally backed by the wood products industry, and even though SFI has distanced itself from the logging industry, critics still say it is less rigorous than FSC.Things get ugly between FSC and SFI when LEED gets factored in. LEED is the U.S. Green Building Council’s rating system for buildings, and they currently give points only for FSC wood, not SFI. SFI representatives grumble that this is hurting the domestic lumber industry, but… well, if you’re really interested you can read all about the “Wood Wars” at BuildingGreen.You will now understand my next haiku: Can’t decide between FSC and SFI? Just build out of rocks. Heat-recovery ventilation A punch in the nose To the next one who tells me “A house has to breathe.”Whenever I tell people we’re building an extremely tight house, someone always pipes up, “Well, a house has to breathe.” Yes, and that’s why we’re installing a ducted heat recovery ventilator (HRV). An HRV is a a fresh-air system with pipes to the outside, and it has a heat exchanger that transfers most of the heat between the two streams.Our HRV is 84% efficient, which means that in cold weather it will transfer 84% of the heat from the outgoing stale airstream into the incoming fresh airstream. Compare this to a leaky house, which gets fresh air and expels stale air through holes in the building envelope, losing oodles of heat in the process.Lately when people tell me a house has to breathe, I tell them that a human also has to breathe but we do it with lungs and a respiratory system rather than by punching holes all over our body. For some reason, this metaphor really makes an impression. Passive solar orientationI already covered passive solar orientation in another blog post, so I’ll skip straight to the haiku: Squinting and roasting As the western light shines in. But look at the view!The point here is that west-facing windows become a problem during the summer as the sun begins to set, filling the room with unwanted heat and glare. Sadly, most builders ignore passive solar principles when siting a house, instead placing windows toward the best view. Andrea Lemon lives in Brattleboro, Vermont. She and her husband Ted Lemon write the Almost Passive House blog.