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8+ years building in West Michigan · Fixed-price contracts (the quote is the price) · 3D design sketch on the first visit · 2-year workmanship warranty · 4.7★ on Google (19 reviews)
True 4-season sunrooms built for Michigan winters — insulated walls, engineered Low-E argon glass, frost-protected foundations, and HVAC tied into the main house. Three-season builds when you want the open-air feel without the year-round cost. Gable, shed, conservatory, lean-to, or fully integrated home additions that read as part of the original architecture.
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619 36th St SW, Wyoming, MI 49509 · Roughly 10 to 25 minutes from most Grand Rapids addresses. By appointment only — we come to you for in-home consultations. · Open in Google Maps →
A sunroom is one of the most over-promised and under-built additions in the West Michigan market. Aluminum-frame kits, franchise enclosures, and Pella-style add-ons all sell the same dream and most of them sit empty from December through March. Four real things separate a Thornapple sunroom build from everything else for sale in Grand Rapids.
Every Thornapple four-season sunroom is built to the same wall, roof, and foundation standard as the rest of your house. Full R-19 to R-21 insulated walls. R-30 to R-38 insulated ceiling. Double-pane Low-E argon glass minimum, triple-pane on north and west exposures. Frost-protected shallow foundation or full crawl tied to the existing structure. HVAC integration that holds the room at 70 degrees in January and 72 in July. The result is a room you actually use every month of the year — not a four-season name on a three-season build.
Aluminum-frame prefab kits read as an enclosure bolted to the back of a house. Our sunrooms read as part of the original architecture — matched siding, matched roofline, matched trim package, matched flooring, matched ceiling height where the geometry allows. You can stand in the front yard and not be able to tell which part of the house is the addition. That integration is what holds resale value and what makes the room actually feel like a room rather than a porch you closed in.
An estimate is a guess. A fixed-price contract is binding. On a sunroom that runs $80K to $250K with custom glass packages, structural tie-ins, and HVAC integration, that distinction is the single most important protection you have. The number we put in writing after the design phase is the number you pay — no allowance games, no surprise change orders, no end-of-project reconciliation. The only way it moves is if you choose to change scope. See how the process works.
Our in-home Grand Rapids consultation is a working session, not a sales pitch. We measure your lot, the back of your house, the view you're chasing, and the part of the existing structure the sunroom will tie into. We model the addition in real-time 3D in your living room and hand back an honest budget range tied to actual scope choices — configuration, glass package, foundation type, HVAC approach — before you commit to anything. You walk away knowing what's buildable on your specific lot and what it would cost.
This is the decision that sets the budget, the timeline, the foundation type, the glass spec, the HVAC plan, and how many months a year you'll actually use the room. We work through it honestly in discovery before any number gets locked in.
A three-season sunroom runs roughly April through October in Grand Rapids — through the seasons where you'd be comfortable in a heavy sweater on the worst day. Single-pane or basic double-pane glass. No insulated walls or roof. No HVAC integration. Typically a floating slab foundation that doesn't rigidly tie to the main house, so frost heave isn't a concern. Reads as a covered porch architecturally and counts as semi-conditioned space on the appraisal — meaningful but not full living square footage. Build time of six to ten weeks. Cost band of $40,000 to $80,000. The right choice when you want morning coffee with the view from May through September, you don't need it in February, and you want to keep the budget contained.
A four-season sunroom is built to the same standard as any other room in your house. Full insulation in walls and ceiling. Engineered glass package with U-value at or below 0.30 and proper SHGC for orientation. Frost-protected shallow foundation or full crawl tied into the main-house structure. HVAC extension or dedicated mini-split heat pump so the room sits at 70 degrees year-round. Reads as integrated home architecture. Counts as finished living square footage on the appraisal. Build time of ten to sixteen weeks. Cost band of $80,000 to $175,000. The right choice when you want to use the room every month, you want the addition to hold resale value, and you're planning to stay in the home long-term.
For most Grand Rapids homeowners staying in the home for the next 10+ years, the four-season pencils out. The cost delta over a three-season is real — usually 60 to 100 percent more — but you're buying twice the usable year and full resale value on the additional square footage. For homeowners planning to sell in three to five years, the three-season can make sense as the better return per dollar.
The single most common reason a "four-season" sunroom in West Michigan sits empty in February: the glass is wrong. Single-pane and basic double-pane glass run an R-value of 1 to 2 — for context, an insulated framed wall in your house is R-19 to R-21. A sunroom with thirty linear feet of single-pane glass is leaking more heat than the rest of your house combined, and the HVAC fights a losing battle against the cold radiating off the glass surface.
Double-pane Low-E argon is the four-season minimum — R-3 to R-4 effective, U-value around 0.30, and a Solar Heat Gain Coefficient (SHGC) in the 0.30 to 0.40 range for south and west glazing. That's what makes the room actually feel warm in January instead of cold-glass-radiant-discomfort warm.
Triple-pane Low-E argon with two suspended films is the upgrade — R-5 to R-7, U-value 0.20 or better, and the standard we recommend for north and west exposures or for higher-finish homes where the sunroom faces the worst weather. Material adder of 25 to 40 percent over double-pane. On a 200-square-foot sunroom that's $4,000 to $8,000 — and it pays back across the 25-to-30-year ownership window in heating cost, comfort, and resale.
The right glass spec is orientation-specific — we run the heat-loss math against your specific elevation, sun exposure, and tree cover before recommending a package. There is no one-size-fits-all four-season glass spec in Michigan. Anyone selling you one is selling you a quote, not a build.
Glass gets the attention. Foundation and HVAC integration are what actually make the room usable every month of the year. Kent County frost depth is 42 inches — every four-season sunroom foundation either reaches below that line or uses frost-protected design to keep the frost line away from the footings.
Acceptable for three-season builds because the room is not rigidly tied to the main house structure — frost heave can move the slab without damaging anything. Not recommended for any four-season build in Michigan. Lowest-cost foundation option but limits the build to the cheapest sunroom category.
Rigid foam insulation extending outward from the footing prevents the frost line from reaching the foundation. Allows footings at 16 to 24 inches deep rather than the standard 42 inches. Roughly a $5,000 to $10,000 adder over a slab. The most cost-effective Michigan-compliant foundation for a stand-alone four-season sunroom on appropriate soils.
The standard build for four-season sunrooms tied into a main-house crawl or basement. Allows HVAC runs, plumbing, and electrical to integrate cleanly with the existing systems. Frost-depth-compliant by default. Adds about $10,000 to $20,000 over a slab depending on size and depth. The most common four-season foundation choice we build.
Where the existing house has a finished basement and the geometry works, extending the basement under the sunroom captures additional finished living square footage at a fraction of the cost of building it later. Premium spec, premium investment — only makes sense on a subset of homes but unbeatable when it does.
A 9,000 to 12,000 BTU mini-split heat pump covers a 150-to-250-square-foot four-season sunroom — independent heating and cooling control, two-day install, $3,000 to $6,000 including line set and electrical. The right option for almost every four-season sunroom because solar heat gain swings the load wildly between morning and afternoon and a dedicated unit handles that load without taxing the main HVAC.
Extending the main HVAC system to serve the sunroom runs $4,000 to $10,000 depending on duct-run distance and whether the existing system has spare capacity. Common when the sunroom is one room of a larger primary suite or great room addition where the duct run is short and the system has headroom.
In-floor radiant electric or hydronic heat at $8,000 to $15,000 for a 200-square-foot sunroom. Premium spec, premium feel — warm tile under your feet in February. Almost always paired with a mini-split for cooling on hot summer days. The high-finish four-season standard for homes where the sunroom sees heavy year-round use.
A four-season sunroom roof carries the same insulation spec as a primary house roof — R-30 minimum in Michigan, R-38 preferred. Closed-cell spray foam under the roof deck is the high-performance option that also air-seals the assembly. The roof is where most prefab kits fall apart — aluminum-frame roof panels at R-15 are not four-season construction.
The shape is an architectural choice driven by your existing roofline, your view, and how you want the addition to read from the street. The construction standard underneath is the same Thornapple spec on all five.
Pitched roof with a vaulted interior ceiling. Best for matching the existing roofline on a Cape Cod, colonial, or two-story home where the addition needs to carry the same roof geometry as the main house. Higher cost than a shed roof because of the framing complexity, but the architectural payoff is real — the sunroom reads as original from the street.
Single-slope roof from the main house eave outward. The most common and most cost-effective four-season configuration — ties cleanly into existing roof framing and works on virtually every home style. Best when the addition will sit at the back of the house where the roof line isn't visible from the street.
Heavy glazing on the roof and walls — dramatic, high-light, high-premium. Requires careful summer heat-gain management and reads as a feature room rather than a normal addition. Best for view properties (river, lake, woods) where the glass roof is part of the point. Glass-roof complexity adds cost; expect a 25 to 40 percent premium over an equivalent-size shed-roof build.
Single-slope shed off the main house, often more three-season-leaning. Lower-cost build, simpler structural tie-in, and a strong choice for homeowners who want the open-air sunroom feel without committing to four-season construction. Common on ranch-style homes where the existing roof line allows a clean addition.
The configuration we build most often when the homeowner wants the room to look like part of the original house. Matched roofline, matched siding, normal exterior — with maximum glazing on the view side. From the street, you can't tell it's a sunroom. From inside, it's a glass-walled great room. The "you can't tell it's an addition" approach — Thornapple's signature on most home additions.
A sunroom paired with a kitchen extension, mudroom, or primary suite expansion as a single addition project. The sunroom carries the view glazing, the adjacent room carries the more typical wall and window spec. Often the highest-ROI configuration because the construction overhead spreads across more usable square footage. Common pairing with our kitchen remodel or complete home remodeling work.
Five phases, no surprises. Every one documented in your project portal so you always know where you are.
Want more detail on any phase? Read the full design-build remodeling process — or jump straight to booking a discovery call.
Below are honest 2026 ranges for Grand Rapids, East Grand Rapids, Forest Hills, Ada, Cascade, Kentwood, Wyoming, Caledonia, Grandville, and surrounding West Michigan. Pricing depends on configuration, size, glass package, foundation type, and HVAC approach. Final pricing locks into a fixed-price contract after design. For the broader Grand Rapids-area cost breakdown, read our full home addition cost guide or run a quick estimate in the cost estimator.
Floating slab, single or basic double-pane glass, no insulation, no HVAC. Usable April through October. Reads as a covered porch architecturally. The lowest-cost sunroom build and the right choice when you want the open-air feel and don't need the room in winter.
Full insulation package, double-pane Low-E argon glass, frost-protected shallow foundation or full crawl, mini-split HVAC. Shed-roof configuration off the main house eave. The most common four-season build — year-round use, full resale value as conditioned living space.
Pitched roof matching the existing home, vaulted interior ceiling, full four-season construction spec. Premium over a shed roof because of the framing complexity — but the architectural integration is unmatched for Cape Cod, colonial, and two-story homes.
Heavy glazing on roof and walls, dramatic high-light interior. Glass-roof complexity, triple-pane premium glass on most exposures, careful summer heat-gain management. The high-finish four-season choice for view properties where the glass roof is part of the point.
The addition reads as part of the original house from the street — matched roofline, matched siding, normal exterior — with maximum glazing on the view side. The "you can't tell it's a sunroom" approach. Highest architectural integration, highest resale value.
The Grand Rapids three-season range. Lower end for slab-on-grade lean-to builds, upper end for larger footprints with quality double-pane glass and finished interior.
The Grand Rapids four-season range. Lower end for shed-roof builds with double-pane Low-E argon glass and mini-split HVAC. Upper end for gable, conservatory, or integrated builds with triple-pane glass and full HVAC integration. The high-finish, view-property number can push past $500 per square foot.
A 144-square-foot shed-roof four-season sunroom — the most common smaller-footprint Grand Rapids build. Mini-split HVAC, double-pane Low-E argon glass, frost-protected foundation. Compact but fully four-season.
A 224-square-foot shed or gable four-season sunroom — the most common mid-size build. Generous enough to seat a full living-room layout, mid-pane glass, full HVAC integration. The sweet-spot sizing for most Grand Rapids homeowners.
A 400-square-foot four-season build — large enough to function as a primary great-room expansion, often paired with a kitchen extension or adjacent mudroom. Triple-pane glass on heavy-exposure elevations, full crawl foundation, possible duct extension from main HVAC.
HOA architectural review, site plan review, and view-specific glass packages (heavy north or west exposure, lake or wooded views) can move pricing inside or above these ranges. We plan for that in discovery and price it into the fixed contract — it doesn't become a surprise change order mid-build.
A sunroom over 200 square feet, or any sunroom structurally tied to the main house, triggers a building permit in every Kent County jurisdiction we serve. Electrical, mechanical (HVAC), and plumbing permits follow as triggered by scope — a four-season sunroom with mini-split HVAC, electrical, and integrated lighting will require all of them.
Larger footprints, lot coverage approaching the maximum, drainage impacts, or setback proximity can trigger site plan review before permits issue. That adds roughly four to eight weeks to the pre-construction timeline. Some Forest Hills, East Grand Rapids, Ada, and Cascade neighborhoods carry HOA architectural review committee (ARC) approval requirements that have to clear before township submission — another two to six weeks depending on the HOA's review schedule.
Ada Township is the only Kent County jurisdiction with an unusual permit pathway — Ada contracts with Cascade Township for permit issuance and inspections, so the application routes through Cascade. We handle that pathway end-to-end. Detail on our Ada home addition page.
Thornapple handles every step of that pathway as part of the fixed-price contract — township submission, site plan review coordination, HOA ARC submission and follow-up, every inspection through final. You don't step into a building department. Read more on our Grand Rapids remodeling permits guide.
Real Thornapple sunroom projects from Grand Rapids-area homes. Descriptive names — no client names, no street addresses. See the design intent, the integration with the existing structure, and the four-season construction at work.
An insulated four-season sunroom built to be used every month of the year. Scope: full HVAC tie-in to the main house, engineered double-pane Low-E argon glass package, properly sized header and structural support, finished interior with trim level matching the rest of the home, and exterior siding and roofline carried over so the room reads as original.
A gable-roof four-season sunroom matched to an existing colonial home. Scope: pitched roof carried from the main structure, vaulted interior ceiling, full R-21 wall insulation and R-38 ceiling, structural tie-in designed so the addition reads as original architecture from the street, and full mechanical integration with the existing HVAC.
A heavy-glazing four-season sunroom positioned to capture wooded-lot views year-round. Scope: triple-pane Low-E argon glass on the north exposure for heat-loss control, mini-split heat pump for independent climate control, in-floor radiant heat tile floor, and integrated trim and flooring carried from the main house so the addition feels like a continuation of the home rather than a tacked-on room.
“Nate and Austin are great to work with, can pivot throughout the project and address obstacles that sometimes arise. Communication was constant and the result was exactly what we asked for.”
“More than accommodating, professional, personable, and kept me updated every step of the way. Communication and work completed was high quality.”
“Incredible! Reliable, friendly, hardworking, passionate about their work. Highly recommended.”
Sunroom additions are most commonly built in Grand Rapids' surrounding higher-finish neighborhoods — lots large enough to support a meaningful addition, homes with the architectural character to integrate one, and homeowners staying in the home long-term. From our Wyoming office, we cover the full Kent County market.
A meaningful share of the sunroom additions we build are not for the next five years — they're for the next thirty. The view, the wooded lot, the river, the neighbors you've known a decade, the school district that finished raising the kids — none of that needs to change. What needs to change is having a room that earns its keep every month of the year. A morning coffee room. A year-round plant room. A dedicated quiet sitting room facing the woods. An expanded great room for grandchildren visits. A ground-floor sitting room you can still use comfortably when stairs become harder.
We design for that future intentionally. Ground-floor placement so the room is accessible at every life stage. Wider doorways and clear circulation for mobility decades from now. Comfort-height fixtures and reinforced wall blocking where grab bars might eventually go — designed in, never bolted on later. Glass packages chosen with twenty-year cost-of-ownership math, not first-year sticker price. Foundation systems that won't fail in year fifteen.
Done right, you won't see the planning — you'll see a Grand Rapids home that simply feels good, at fifty, at seventy, at every stage in between. The aging-in-place framework is detailed on our accessibility remodeling in Grand Rapids page. Multi-generational scope often expands into in-law suite additions where the sunroom is one room of a larger build.
The real questions Grand Rapids homeowners ask before committing to a sunroom addition — not the generic ones the franchise enclosure brands recycle.
Grand Rapids sunroom additions typically run from $40,000 for a small three-season build up to $250,000+ for a large four-season conservatory or integrated home addition. The bands we see most often: three-season sunrooms $40,000 to $80,000; four-season sunrooms $80,000 to $175,000; integrated room additions with sunroom features $125,000 to $250,000+. The per-square-foot benchmark is $200 to $300 for three-season and $350 to $500 for four-season — the four-season number is higher because of full insulation, engineered glass, frost-protected foundation, and HVAC integration. Every Thornapple project locks at a fixed-price contract once scope is finalized — the price we quote is the price you pay. Full breakdown in our home addition cost guide.
A three-season sunroom is usable roughly April through October — single-pane or basic double-pane glass, no insulated walls or roof, no HVAC, typically a floating slab foundation. Reads as a covered porch and adds limited resale value because it does not count as conditioned living space. A four-season sunroom is built to be used every month of the year — full R-19 to R-21 insulated walls, R-30 to R-38 insulated ceiling, double-pane Low-E argon glass minimum (triple-pane for north or west exposure), frost-protected shallow foundation or full crawl tied into the main house, HVAC duct extension or dedicated mini-split. Counts as finished living square footage and carries real resale value. In Grand Rapids, the four-season is what most homeowners actually want because the three-season sits empty for half the year.
Yes, in nearly every Kent County jurisdiction. A sunroom over 200 square feet, or any sunroom structurally tied to the main house, triggers a building permit. Electrical, mechanical, and plumbing permits follow the scope — a four-season sunroom with HVAC and lighting needs all of them. Larger footprints or setback proximity can trigger site plan review (four to eight weeks pre-construction). Some Forest Hills, Ada, and East Grand Rapids neighborhoods require HOA architectural review committee (ARC) approval before township submission. Thornapple handles every step of that pathway end-to-end as part of the fixed-price contract. Full detail on our remodeling permits guide.
For a four-season sunroom in Grand Rapids, double-pane Low-E argon glass is the minimum — R-3 to R-4 effective insulation, U-value around 0.30, SHGC 0.30 to 0.40 for south and west glazing. For north and west exposures, or high-finish homes facing the worst weather, we move to triple-pane Low-E argon with two suspended films: R-5 to R-7, U-value 0.20 or better. Triple-pane carries a 25 to 40 percent material adder over double-pane — on a 200-square-foot sunroom that's $4,000 to $8,000 — and it pays back in heating cost and comfort across the 25-to-30-year ownership window. The glass package is the single most important spec decision on a Michigan four-season sunroom. Cheap glass is the single biggest reason "four-season" rooms sit empty in February.
For a three-season build, a floating slab on grade is acceptable. For a four-season build, three options: a frost-protected shallow foundation (FPSF) with a $5,000 to $10,000 adder over slab; a full crawl space tied into the main-house crawl or basement ($10,000 to $20,000 adder); or a full basement extension where the existing basement is finished and the geometry works. Frost depth in Kent County is 42 inches — every four-season foundation needs to reach below that line or use FPSF rigid insulation to keep the frost line away from the footings. The right choice depends on soil conditions, drainage, water table, and existing foundation type — we work through it in the design phase before pricing locks.
Three options. A dedicated mini-split heat pump — recommended on most Grand Rapids four-season sunrooms: 9,000 to 12,000 BTU covers a 150-to-250-square-foot room, two-day install, $3,000 to $6,000 including line set and electrical, independent climate control that doesn't tax the main HVAC. A main HVAC duct extension — $4,000 to $10,000 depending on duct-run distance and whether the existing system has spare capacity. In-floor radiant heat — $8,000 to $15,000 for a 200-square-foot sunroom, premium spec, almost always paired with a mini-split for cooling. The mini-split-plus-radiant combination is the high-finish four-season standard for homes where the sunroom sees heavy year-round use.
It depends on the existing roofline and how you want the addition to read. Gable-roof matches Cape Cod and colonial roof geometry — pitched roof, vaulted interior, premium architectural integration. Shed-roof is the most common and most cost-effective four-season configuration — clean tie-in to existing eave. Conservatory carries heavy glass on the roof — dramatic, high-premium, requires careful summer heat-gain management. Lean-to is a single-slope three-season-leaning option. And the configuration we build most often for Grand Rapids homeowners who want the room to look like part of the original house is the integrated home addition — matched roofline, matched siding, normal exterior, maximum glazing on the view side. From the street, you can't tell it's a sunroom. We model all five options in 3D during the design phase before any commitment.
From permit issuance to final walkthrough, a three-season sunroom runs six to ten weeks. A four-season sunroom runs ten to sixteen weeks because of the additional foundation work, full mechanical integration, insulation and air sealing, and glass package lead time on triple-pane orders. Design and permitting add roughly six to twelve weeks before construction begins — longer if site plan review is required by the township or HOA ARC approval applies. End to end: four to seven months for a four-season build. Every milestone is mapped in the fixed-price contract and tracked daily in your project portal. We typically start four-season builds in mid-summer to be enclosed by first frost so interior trim and finish happens through fall and winter.
For most Grand Rapids homeowners staying in the home long-term, yes. A prefab aluminum-frame kit or franchise enclosure runs $25,000 to $60,000 versus $80,000+ for a custom four-season build — cheaper and faster up front. But the trade-off is real. Prefab kits use lighter framing and lower-spec glass that struggle in Michigan winters, the room reads as a tacked-on aluminum enclosure rather than part of the original house, and resale value is limited because the room rarely counts as conditioned living space on the appraisal. A custom design-build sunroom — same wall, roof, foundation, and finish standards as the rest of your house — integrates architecturally, holds full resale value as finished square footage, and is built to last as long as the original home. For homeowners planning to sell in three to five years, a high-spec prefab can pencil out. We'll tell you which fits in the first conversation.
Our full home addition page — scope, process, what's included, and FAQs.
Real Grand Rapids-area addition costs broken down by scope, size, and finish level.
How permits work across Grand Rapids, Cascade, Ada, Forest Hills, and EGR — written for homeowners, not contractors.
Designing sunrooms and additions for the next thirty years of ownership.
Run a quick range for your specific sunroom scope before booking the discovery call.
Real Thornapple projects across West Michigan — sunrooms, additions, kitchens, bathrooms, and full-home remodels.
Sunroom additions are one piece of our design-build remodeling in Grand Rapids practice — design, build, and budget under one roof. Sunroom work often pairs with broader Grand Rapids remodeling scope.
When every room needs attention, you need a partner who coordinates every trade, timeline, and detail.
A kitchen that finally works for you — from 3D design to expert installation, protected from start to finish. Often paired with adjacent sunroom builds.
Fixed-price bathroom remodels in Grand Rapids — primary baths, guest baths, accessibility, basement bath builds.
It starts with a free discovery call — a quick conversation to talk through your project, get honest answers about three-season versus four-season, glass and foundation choices, and what it would cost to build on your specific lot. No commitment. No pressure. Just clarity.
Book Your Free Discovery CallOr call us at (616) 404-3400
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