diff --git a/src/ifcgeom/ConversionSettings.h b/src/ifcgeom/ConversionSettings.h
index f49941ec4b..544c04ffe3 100644
--- a/src/ifcgeom/ConversionSettings.h
+++ b/src/ifcgeom/ConversionSettings.h
@@ -312,6 +312,12 @@ namespace ifcopenshell {
 				static constexpr bool defaultvalue = false;
 			};
 
+			struct NoParallelMapping : public SettingBase<NoParallelMapping, bool> {
+				static constexpr const char* const name = "no-parallel-mapping";
+				static constexpr const char* const description = "Perform mapping upfront (single-threaded) as opposed to in parallel. May decrease performance, but also decrease output size (in the future)";
+				static constexpr bool defaultvalue = false;
+			};
+
 			struct ForceSpaceTransparency : public SettingBase<ForceSpaceTransparency, double> {
 				static constexpr const char* const name = "force-space-transparency";
 				static constexpr const char* const description = "Overrides transparency of spaces in geometry output.";
@@ -440,7 +446,7 @@ namespace ifcopenshell {
 		};
 
 		class IFC_GEOM_API Settings : public SettingsContainer<
-                                          std::tuple<MesherLinearDeflection, MesherAngularDeflection, ReorientShells, LengthUnit, PlaneUnit, Precision, OutputDimensionality, LayersetFirst, DisableBooleanResult, NoWireIntersectionCheck, NoWireIntersectionTolerance, PrecisionFactor, DebugBooleanOperations, BooleanAttempt2d, WeldVertices, UseWorldCoords, UseMaterialNames, ConvertBackUnits, ContextIds, ContextTypes, ContextIdentifiers, IteratorOutput, DisableOpeningSubtractions, ApplyDefaultMaterials, DontEmitNormals, GenerateUvs, ApplyLayerSets, UseElementHierarchy, ValidateQuantities, EdgeArrows, BuildingLocalPlacement, SiteLocalPlacement, ForceSpaceTransparency, CircleSegments, KeepBoundingBoxes, PiecewiseStepType, PiecewiseStepParam>
+                                          std::tuple<MesherLinearDeflection, MesherAngularDeflection, ReorientShells, LengthUnit, PlaneUnit, Precision, OutputDimensionality, LayersetFirst, DisableBooleanResult, NoWireIntersectionCheck, NoWireIntersectionTolerance, PrecisionFactor, DebugBooleanOperations, BooleanAttempt2d, WeldVertices, UseWorldCoords, UseMaterialNames, ConvertBackUnits, ContextIds, ContextTypes, ContextIdentifiers, IteratorOutput, DisableOpeningSubtractions, ApplyDefaultMaterials, DontEmitNormals, GenerateUvs, ApplyLayerSets, UseElementHierarchy, ValidateQuantities, EdgeArrows, BuildingLocalPlacement, SiteLocalPlacement, ForceSpaceTransparency, CircleSegments, KeepBoundingBoxes, PiecewiseStepType, PiecewiseStepParam, NoParallelMapping>
 		>
 		{};
 }
diff --git a/src/ifcgeom/Iterator.h b/src/ifcgeom/Iterator.h
index f4f4649b7c..8bf862def1 100644
--- a/src/ifcgeom/Iterator.h
+++ b/src/ifcgeom/Iterator.h
@@ -88,8 +88,15 @@
 namespace {
 	struct geometry_conversion_result {
 		int index;
+
+		// For NoParallelMapping==true
 		ifcopenshell::geometry::taxonomy::ptr item;
 		std::vector<std::pair<const IfcUtil::IfcBaseEntity*, ifcopenshell::geometry::taxonomy::matrix4::ptr>> products;
+
+		// For NoParallelMapping==false
+		IfcUtil::IfcBaseEntity* representation;
+		aggregate_of_instance::ptr products_2;
+
 		std::vector<IfcGeom::BRepElement*> breps;
 		std::vector<IfcGeom::Element*> elements;
 	};
@@ -199,20 +206,26 @@ namespace IfcGeom {
 
 			for (auto& task : reps) {
 				geometry_conversion_result res;
-				res.item = converter_->mapping()->map(task.representation);
-				if (!res.item) {
-					continue;
+				res.index = task.index;
+				if (!settings_.get<ifcopenshell::geometry::settings::NoParallelMapping>().get()) {
+					res.representation = task.representation;
+					res.products_2 = task.products;
+				} else {
+					res.item = converter_->mapping()->map(task.representation);
+					if (!res.item) {
+						continue;
+					}
+					std::transform(task.products->begin(), task.products->end(), std::back_inserter(res.products), [this, &res](IfcUtil::IfcBaseClass* prod) {
+						auto prod_item = converter_->mapping()->map(prod);
+						return std::make_pair(prod->as<IfcUtil::IfcBaseEntity>(), ifcopenshell::geometry::taxonomy::cast<ifcopenshell::geometry::taxonomy::geom_item>(prod_item)->matrix);
+					});
 				}
-				std::transform(task.products->begin(), task.products->end(), std::back_inserter(res.products), [this, &res](IfcUtil::IfcBaseClass* prod) {
-					auto prod_item = converter_->mapping()->map(prod);
-					return std::make_pair(prod->as<IfcUtil::IfcBaseEntity>(), ifcopenshell::geometry::taxonomy::cast<ifcopenshell::geometry::taxonomy::geom_item>(prod_item)->matrix);
-				});
 				tasks_.push_back(res);
 			}
 
 			size_t num_products = 0;
 			for (auto& r : tasks_) {
-				num_products += r.products.size();
+				num_products += !settings_.get<ifcopenshell::geometry::settings::NoParallelMapping>().get() ? r.products_2->size() : r.products.size();
 			}
 
 			time_points[2] = high_resolution_clock::now();
@@ -510,7 +523,17 @@ namespace IfcGeom {
 			ifcopenshell::geometry::Settings settings,
 			geometry_conversion_result* rep)
 		{
-			auto representation = rep->item;
+			if (!settings_.get<ifcopenshell::geometry::settings::NoParallelMapping>().get()) {
+				rep->item = kernel->mapping()->map(rep->representation);
+				if (!rep->item) {
+					return;
+				}
+				std::transform(rep->products_2->begin(), rep->products_2->end(), std::back_inserter(rep->products), [this, &rep, kernel](IfcUtil::IfcBaseClass* prod) {
+					auto prod_item = kernel->mapping()->map(prod);
+					return std::make_pair(prod->as<IfcUtil::IfcBaseEntity>(), ifcopenshell::geometry::taxonomy::cast<ifcopenshell::geometry::taxonomy::geom_item>(prod_item)->matrix);
+				});
+			} else {
+			}
 
 			auto product_node = rep->products.front();
 			const IfcUtil::IfcBaseEntity* product = product_node.first;
@@ -518,8 +541,8 @@ namespace IfcGeom {
 
 			Logger::SetProduct(product);
 			
-			IfcGeom::BRepElement* brep = static_cast<IfcGeom::BRepElement*>(decorate_with_cache_(GeometrySerializer::READ_BREP, (std::string)product->get("GlobalId"), std::to_string(representation->instance->as<IfcUtil::IfcBaseEntity>()->id()), [kernel, settings, product, place, representation]() {
-				return kernel->create_brep_for_representation_and_product(representation, product, place);
+			IfcGeom::BRepElement* brep = static_cast<IfcGeom::BRepElement*>(decorate_with_cache_(GeometrySerializer::READ_BREP, (std::string)product->get("GlobalId"), std::to_string(rep->item->instance->as<IfcUtil::IfcBaseEntity>()->id()), [kernel, settings, product, place, rep]() {
+				return kernel->create_brep_for_representation_and_product(rep->item, product, place);
 			}));
 
 			if (!brep) {
@@ -539,7 +562,7 @@ namespace IfcGeom {
 				const IfcUtil::IfcBaseEntity* product2 = p.first;
 				const auto& place2 = p.second;
 
-				IfcGeom::BRepElement* brep2 = static_cast<IfcGeom::BRepElement*>(decorate_with_cache_(GeometrySerializer::READ_BREP, (std::string)product2->get("GlobalId"), std::to_string(representation->instance->as<IfcUtil::IfcBaseEntity>()->id()), [kernel, settings, product2, place2, representation, brep]() {
+				IfcGeom::BRepElement* brep2 = static_cast<IfcGeom::BRepElement*>(decorate_with_cache_(GeometrySerializer::READ_BREP, (std::string)product2->get("GlobalId"), std::to_string(rep->item->instance->as<IfcUtil::IfcBaseEntity>()->id()), [kernel, settings, product2, place2, brep]() {
 					return kernel->create_brep_for_processed_representation(product2, place2, brep);
 				}));
 				if (brep2) {