Why does sun angle matter so much for a pit greenhouse?
A pit greenhouse trades light for warmth. The earth around it holds heat and cuts wind, but the south wall of the pit blocks low winter sun. How much it blocks depends on one number: the sun's altitude at solar noon.
The formula is simple. Solar noon altitude = 90° − latitude + solar declination. On December 21 the declination is −23.44°. For Wichita at 37.69°N:
90 − 37.69 − 23.44 = 28.87°
A wall of height H casts a noon shadow of H ÷ tan(altitude). At 28.87°, tan = 0.552, so the shadow is 1.81 × H. A 4-foot pit wall shades 7.3 feet of floor. An 8-foot wall shades 14.5 feet.
Wichita gets 1.4° more December sun than Kansas City (27.5°). That sounds small. It cuts the shade ratio from 1.92 to 1.81, which is about 6% less shadow on the same pit. The sun-angle guide compares Minneapolis and La Paz too.
Where do walipini plans come from, and why don't they fit Wichita as drawn?
Most "walipini" plans online trace back to Walipini Construction, a 2002 bulletin from the Benson Agriculture and Food Institute at Brigham Young University, written for La Paz, Bolivia at 16.4°S. It describes a hole 6 to 8 feet deep, plus 1 to 2 feet for drainage gravel and topsoil. In La Paz the winter sun stands about 50° high, so a deep pit loses little floor to shade.
Bring the same 8-foot pit to Wichita and the December shadow is more than twice as long. The bulletin's roof rule, glazing perpendicular to the winter-solstice sun, also gives a much steeper roof here: 61.1° from horizontal instead of 39–40°. That changes the whole cross-section.
The lesson is not that walipinis fail in Kansas. It is that you cannot copy a Bolivian section drawing and expect Bolivian results.
Deep pit vs. shallow-and-wide: how much floor gets December sun?
We model this with a simple calculation so you can see the trade-off before anyone digs.
Model and assumptions. A pit of width W (measured north to south) and depth D. At solar noon, the south wall casts a shadow D ÷ tan(altitude) across the floor. Lit fraction = max(0, 1 − D ÷ (W × tan(altitude))). This counts only the south wall, only at solar noon, and ignores shading from glazing frames, end walls and snow. Real mornings and afternoons are worse, because the sun is lower.
| December 21, solar noon | Deep pit (8 ft deep × 16 ft wide) | Shallow-and-wide (4 ft deep × 20 ft wide) |
|---|---|---|
| Shadow length | 14.5 ft | 7.3 ft |
| Floor lit (Wichita, 28.87°) | 9% | 64% |
Worked example for the deep pit in Wichita: 1 − 8 ÷ (16 × 0.552) = 1 − 0.906 = 0.094, or about 9%. For the shallow pit: 1 − 4 ÷ (20 × 0.552) = 1 − 0.362 = 0.64.
At the darkest point of the year, the deep pit has almost no direct sun on its floor at noon. The shallow-and-wide pit keeps nearly two-thirds of its floor in sun. In January the numbers improve to 21% and 68%. By March they reach 61% and 85%. The sun-angle guide has every month.
You still get earth contact, a north berm and wind shelter at 4 feet. Going to 8 feet doubles the excavation and the wall height you have to retain, and it buys that extra earth contact with most of your December floor sun.
How we design an earth-sheltered greenhouse for Wichita
Our design approach follows the numbers above:
- Long axis east-west. The glazed face points due south to catch the low winter arc.
- Shallow excavation, 3–4 ft typical. Enough to get earth contact and wind shelter without burying the floor in shade.
- Earth berm on the north, east and west. Excavated soil goes back as a berm instead of off-site, where your soil allows it.
- Steep south glazing. We start near 61° for maximum December gain and adjust for your growing season. See passive solar greenhouse design for the trade-offs.
- Reflective north wall. A light-colored or reflective north wall bounces light back onto beds.
- Thermal mass and optional air storage. Water barrels, a masonry north wall or a climate battery can add stored heat.
- Impact-rated glazing. Wichita has a long hail record, so glazing choices follow our hail-resistant glazing guide.
Excavation is scoped per site. Timing depends on season, soil conditions, permits and materials; your quote gives a schedule.
What Wichita soils and water mean for a below-grade build
This is the part generic plans skip. Sedgwick County has three very different conditions under it.
Arkansas River valley: watch the seasonal water table
Much of the river valley is sandy alluvium. NRCS soil survey data for Sedgwick County (Soil Data Access) rates the Canadian series itself as well drained. But it often maps alongside the Waldeck series, which is somewhat poorly drained, with a seasonal water table recorded at 61–92 cm (about 2 to 3 feet) from October through April. The "Canadian-Waldeck fine sandy loams" map unit carries a 92 cm minimum water table depth.
October through April is exactly when you want the greenhouse working. A 4-foot pit in a Waldeck inclusion could hold water all winter. We check the soil map for your parcel and, where needed, dig a test hole before committing to depth.
Northwest county: the Equus Beds
Northwest Sedgwick and southwest Harvey County sit over the Equus Beds aquifer, the source of Wichita's municipal well field. USGS notes that Wichita's recharge permits bar artificial recharge in areas where water levels are less than 10 feet below land surface. That tells you the water table there can be shallow. Our Equus Beds water guide covers this in detail.
East and south: shrink-swell clay
East and south of Wichita, soils like Irwin, Tabler and Rosehill are clays with shrink-swell behavior and slow drainage (hydrologic group D) per NRCS data. Clay pushes on retaining walls when wet and pulls away when dry. Below-grade walls here need drainage behind them, a perimeter drain to daylight or a sump, and a wall designed for lateral soil pressure. Our greenhouse foundations page covers footings and drainage.
The west and central upland soils (Blanket, Nalim, Shellabarger) are generally well drained and the easiest ground for a pit. Blanket's clay subsoil still shrinks and swells, so retaining walls there get drainage too.
Radon and air quality
Sedgwick County homes averaged 3.6 pCi/L of radon in 2010 testing, and 30.9% of 3,771 tests were at or above the EPA's 4 pCi/L action level, according to the KDHE county environmental health profile. That's below the Kansas average of 4.8 pCi/L, but it is not zero.
A detached growing space is not a home. But an enclosed, below-grade room with earth walls is the kind of space where soil gas can collect, especially in winter with vents closed. If you plan to spend long hours inside, or attach the greenhouse to your house, test it. A vapor barrier on the floor and earth walls costs little at build time.
Permits and code
Wichita's adopted residential code sets a 24-inch frost depth, with an exemption from frost protection for accessory structures of 400 square feet or less with an eave height of 10 feet or less. Size thresholds for building permits differ between the city (200 sq ft) and unincorporated county (400 sq ft), and a MABCD location permit applies in both. Retaining walls that hold back soil can need engineering of their own, so we raise them with MABCD when we prepare the permit, before anyone digs. See the Wichita greenhouse permit guide before you plan footprint and depth.
What does an underground greenhouse cost in Wichita?
We don't publish a price until we've seen the site. The main cost drivers are:
| Cost driver | Why it matters in Wichita |
|---|---|
| Excavation depth and volume | Each extra foot of depth adds soil to move and wall to retain, and adds shade |
| Soil type | Clay needs drainage and stronger walls; sandy valley soil may need dewatering |
| Retaining wall system | Concrete, block, or treated timber, sized for lateral pressure |
| Glazing | Impact-rated polycarbonate or tempered glass for hail |
| Drainage | Perimeter drain to daylight vs. sump pump |
| Thermal mass or climate battery | Adds cost, adds stored heat |
Published figures for pit (below-grade) greenhouses run about $20–$25 per sq ft (HomeGuide). Russ Finch's roughly 1,200 sq ft geothermal pit greenhouse in Alliance, Neb., cost about $22,000 to build (KCUR, Feb 2016). Those are published figures, not our quote. Our core service area is Sedgwick County and towns within about 30 miles of Wichita; outer-county projects are case by case.
Get a Quote and we'll check your soil map and water table before we talk numbers.
Frequently asked questions
Does an underground greenhouse work in Kansas?
Yes, if it's shaped for Kansas sun. At Wichita's latitude the December noon sun is 28.87° high, so a pit wall shades 1.81 times its height. A shallow, wide pit (about 4 ft deep) keeps most of its floor in winter sun. A deep 8-ft pit keeps very little.
How deep should a walipini be in Wichita?
We usually design for 3 to 4 feet. In our noon-sun model, a 4 ft × 20 ft pit keeps 64% of its floor lit on December 21, while an 8 ft × 16 ft pit keeps 9%. The 6–8 ft depth in the original 2002 Benson Institute plans was designed for La Paz, Bolivia, where the winter sun is much higher.
What angle should the glazing be on an earth-sheltered greenhouse in Wichita?
Glazing perpendicular to the December 21 noon sun sits at 90 − 28.87 = 61.1° from horizontal. That's the same rule the Benson bulletin used for La Paz, applied to Wichita's latitude. Many growers choose a slightly lower angle for better spring and fall performance.
Will groundwater flood an underground greenhouse?
It can in parts of Sedgwick County. NRCS data show a seasonal water table at 2–3 feet in Waldeck soils of the Arkansas River valley, October through April. Northwest county over the Equus Beds can also have shallow water. We check the soil map and dig a test hole where needed.
Do I need to worry about radon in a pit greenhouse?
Test if you'll spend long hours inside or attach it to your home. Sedgwick County homes averaged 3.6 pCi/L in KDHE's 2010 data, with 30.9% of tests at or above 4 pCi/L. A floor vapor barrier is cheap to add during the build.
Is it worth going deeper for more warmth?
Usually not in Wichita. A 3–4 ft pit with a north berm already gives you earth contact and wind shelter. Going deeper adds excavation, retaining wall and drainage cost, and cuts December noon floor sun from 64% (4 × 20 ft pit) to 9% (8 × 16 ft pit) in our model.
Get a quote
Tell us your lot, soil and what you want to grow through the winter. We'll check the soil map, water table and sun geometry, then design an earth-sheltered greenhouse that fits.