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DIY Solar Book, home

Part V: Passive Solar Homes and SunspacesChapter 8. Designing a Passive Solar House

Case-Study Roundup: What Real Owner-Builders Learned

Repeated patterns from solar projects, shown as labeled composites rather than as any real household.

Difficulty
Beginner
Cost
Free
published

Finished projects teach a few lessons over and over. This page states those lessons as composites: invented combinations of ordinary choices and ordinary outcomes. They are not reports of a real house, a real family, or a build you can find in a photo essay. There is no street, no name, and no claim that someone said these words.

If you want a real project, use the links at the bottom and read that project there. Do not treat a composite as a disguise for one of those stories.

The patterns themselves are already in this book. Seal and insulate before you add glass. Give a sunspace one job. Size photovoltaic modules from the bills and the shade, not from the empty look of a roof.

Difficulty

Level
Beginner
Time
Half an hour of reading
Skills
Telling a pattern from a particular house

Cost estimate

Free

Nothing to buy. The composites are here so you can recognize a bad order of work before you spend the money.

Materials

ItemQtyNotes
This page1Three composites. Each one is labeled. None of them is a case file.
The further-reading listOptionalReal projects, written by other people, on other sites. Read them as themselves.

Composite A: glass before the envelope

Picture a cold-climate house that still has a thin attic and a few obvious leaks. The owners, who are not any particular owners, spend their one big season cutting the south wall open and filling it with glass. The glass area lands well above the band on the overhang page, and there is no night cover and no extra mass.

The invented first winter goes like this. Sunny afternoons are too warm. Clear mornings are colder than the old house was, because the new glass is a hole at night and the attic is still a hole all day. The heating system runs hard after sunset. A visitor praises the light and does not see the bill.

The repeatable lesson is the retrofit order. Seal, insulate, shade the glass you already have, then add a modest south opening with an overhang and somewhere for the heat to sit. More glass does not repair a leak.

Composite B: one porch, two jobs

Picture a south porch enclosed with a light plastic cover. A few pots of tender plants sit on the floor. The kitchen door stays open so the afternoon warmth can wander in, and it stays open after dark because nobody built a habit of closing it.

On a clear night in this composite the porch falls toward the outdoor temperature. The open door is then a hole in the house. On a damp afternoon the kitchen side of the wall sweats. The plants still freeze on the night someone tries to harvest the porch until midnight, because the heat was sent indoors and the porch had no water barrels left to give it back.

The lesson is already written: a heating room and a growing room are detailed differently. A heating porch is allowed to go cold after a solid door closes. A growing room keeps its mass and its humidity on its own side of that door. A porch that tries to be both fails at whichever job you forgot.

Composite C: modules before the bill

Picture a south roof with a plumbing vent and a tree that clips one corner for part of the afternoon. The household fills the plane with modules because the roof looked large enough, and they wire them as one series string because that was the diagram on the box. They have not added up a year of kilowatt-hours, and they have not moved the vent or accepted a smaller array.

In the composite, the shaded corner cuts that string for those hours, so the loss is larger than one module. The annual use would have been covered by fewer modules and by shutting off a few loads that run all night. The exciting part, the full roof, was the expensive part.

The lesson is to start from a year of use, then from the shade you actually have, and to treat one shaded module in a series string as a string problem. Landing the conductors still takes an electrician and a permit, and this composite is not a wiring lesson.

Three composites, not three housesThree labeled sketches: seal before adding glass, close a sunspace at night, and size photovoltaic modules from the electric bill.Composite AEnvelope, then glassComposite BOne job for the porchComposite CBills, then modulesThese are invented combinations of common outcomes.Real projects stay in the further-reading links.
Three invented sketches. They are not three houses you can visit, and they are not the projects in the links below.

What shows up in all three

The exciting surface came first: glass, a porch, a roof of modules. The unexciting constraint came later: the attic, the night, the shade, the bill. People who would do it again, in the generic sense this page is willing to claim, would buy the constraint first.

Summer is the other half. A winter heating scheme with no overhang and no plan for west windows becomes a cooling problem in July, so plan summer as part of the same design.

  1. Read the composites as patterns

    Envelope before glass. One job for a sunspace. Bills and shade before modules. If your plan matches a composite, change the plan, not the story.

  2. Do not hunt for the household

    There is not one. Details here are round on purpose so they cannot be a diary.

  3. Use the linked guides for the actual work

    Retrofit order, sunspace planning, overhangs, mass, and photovoltaic sizing. This page does not add a new method.

  4. Open a further-reading link only as that project

    Those pages are other writers and other buildings. Quote them from there if you quote them at all. Do not paste them into this composite.

Further reading

These links go to outside sources. This book cites them by link and does not copy their words or pictures.

General education, not a permit or a stamped design. Follow the safety note in the guide, read the safety disclaimer, and hire a licensed trade when the work requires one.